Wall for catalytic beds of reactors and method for realizing the same

Abstract

Catalytic chemical reactor comprising a perforated wall (6) adjacent to a supporting wall of the reactor or of a catalytic cartridge contained in the reactor, wherein said perforated wall comprises a plurality of panels (7) and comprises first sectors (9) resting on the supporting wall and second sectors (10) spaced from said supporting wall defining a cavity (11), and wherein means are provided for local securing said gas-permeable wall to said supporting wall, said securing means comprising: a plurality of support elements (13) fixed to the supporting wall (4) and passing through respective openings (15) of the first sectors (9) of the gas-permeable wall and a respective plurality of locking elements (14) which can be associated with the said support elements, the panels of the gas-permeable wall being gripped between said supporting wall and said locking elements.

Claims

1. A catalytic chemical reactor comprising a catalytic bed and a gas-permeable wall facing the catalytic bed, wherein: said gas-permeable wall is an assembly of a plurality of panels and each of said panels extends over an angular sector of said permeable wall; the gas-permeable wall comprises first wall sectors which bear against a supporting wall adjacent to the gas permeable wall, and second wall sectors which are spaced from said supporting wall, the first sectors and the second sectors alternating with each other along the circumferential extension of the permeable wall; wherein said supporting wall is cylindrical or substantially cylindrical, wherein said second wall sectors comprise passages for a gas; the reactor further comprising local securing means of said gas-permeable wall to said supporting wall, said securing means comprising: a plurality of supports firmly fixed to the supporting wall and passing through respective openings of the first sectors of the gas-permeable wall; a respective plurality of locking elements which can be associated with said supports, the panels of the gas-permeable wall being clamped between said supporting wall and said locking elements; wherein said panels, being fixed together and secured to the supporting wall, form a single wall element which delimits a catalytic bed; and wherein said gas-permeable wall operates as a gas distributor or collector with respect to a catalytic bed.

2. The reactor according to claim 1, wherein said supporting wall is a shell of said reactor.

3. The reactor according to claim 1, wherein the reactor comprises a catalytic cartridge, said catalytic bed being contained in the cartridge, and said supporting wall being a wall of said cartridge.

4. The reactor according to claim 1, wherein adjacent panels have edges which are at least partially superimposed in the region of the bearing sectors.

5. The reactor according to claim 1, wherein the bearing sectors are formed by reliefs or ribs of the permeable wall.

6. The reactor according to claim 5, said bearing sectors having a V-shaped or trapezoidal cross-section along a sectional plane perpendicular to the axis of the wall.

7. The reactor according to claim 6, wherein said bearing sectors have a V-shaped cross-section which defines a recess for receiving locking elements, and said locking elements have a wedge portion adapted to engage with said recess.

8. The reactor according to claim 1, wherein said bearing sectors comprise a flat surface resting on the supporting wall and the locking elements are formed as flat plates.

9. The reactor according to claim 1, wherein the engagement between the supports fixed to the supporting wall and the respective openings in the bearing sectors of the gas-permeable wall is suitable to allow a movement of the gas-permeable wall with respect to the supporting wall, preferably in an axial direction.

10. The reactor according to claim 1, wherein said supports are threaded pins welded to the supporting wall.

11. The reactor according to claim 1, comprising a plurality of locking elements for each of the bearing sectors, the locking elements of a single bearing sector being aligned along a generatrix of the supporting wall.

12. The reactor according to claim 1, wherein the sectors of the permeable wall have any one of the following configurations: a substantially flat profile, a triangular profile, a curved profile or a circle-arc profile.

13. The reactor according to claim 1, also comprising reinforcing elements of the panels, adapted to withstand the vertical loads, said reinforcements being located preferably in the region of the bearing sectors.

14. A method for realizing a gas-permeable wall inside a chemical reactor, said gas-permeable wall being arranged adjacent to a cylindrical supporting wall of the reactor or of a catalytic cartridge contained in the reactor, and said permeable wall being adapted to form a gas distributor or collector to/from a catalytic bed in the reactor, wherein said permeable wall is an assembly of a plurality of panels, each panel comprising at least a first bearing sector resting on the supporting wall, and a second sector having a perforated surface adapted to passage of gas, wherein the first sector of each panel has a plurality of openings; and wherein the second sector of each panel is spaced from the supporting wall when the panel rests on said supporting wall, the method comprising at least the steps of: a) positioning a first panel adjacent to the supporting wall; b) welding a plurality of pins to the supporting wall through said openings of the bearing sector; c) inserting suitable locking elements and engaging them on said pins so as to secure the panel to the supporting wall; d) repeating the above steps for the following panels until the gas-permeable wall is completed, optionally using an element for closing the wall.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a schematic cross-sectional view of a reactor according to an embodiment of the invention.

(2) FIG. 2 shows partially a perforated wall adjacent to a supporting wall of a catalytic cartridge, according to an embodiment of the invention.

(3) FIG. 3 is a detail of FIG. 2.

(4) FIGS. 4, 5 and 6 show variant embodiments with respect to FIG. 2.

(5) FIG. 7 illustrates an example of embodiment of a closing joint for a wall of the type shown in FIG. 3.

(6) FIG. 8 illustrates an example of embodiment of a closing joint for a wall of the type shown in FIG. 4.

(7) FIG. 9 shows an example of a panel with reinforcements for withstanding the vertical loads.

(8) FIG. 10 shows a cross-section of a panel according to FIG. 9.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(9) FIG. 1 shows schematically a catalytic chemical reactor 1 comprising a shell 2 and a catalytic cartridge 3 inside the shell 2. Said catalytic cartridge has a cylindrical supporting wall 4 and contains a catalyst mass which forms a catalytic bed 5.

(10) The reactor further comprises a gas-permeable wall 6 which in the example acts as a distributor of gas into the catalytic bed 5.

(11) The reactor design of FIG. 1 is inward radial-flow. The flow which passes through the catalytic bed 5 is indicated by the arrows in the figure. Such a reactor is known in the art and does not need to be described in detail.

(12) The gas-permeable wall 6 (FIG. 2) essentially comprises a series of reliefs or ribs 9 which make a bearing contact against the supporting wall 4 of the catalytic cartridge and a series of useful surfaces 10 which are spaced from said supporting wall 4, defining an interspace 11 between the supporting wall 4 and the gas-permeable wall 6.

(13) The ribs 9, according to the example of FIG. 2, have a substantially V-shaped cross-section. The useful surfaces 10 have a plurality of perforations, for example eyelets 12, for allowing the passage of gas.

(14) As seen in the figure, each useful surface 10 is bounded by two adjacent ribs 9. The ribs 9 extend towards the wall 4 and come into direct contact therewith. The ribs 9 and the useful surfaces 10 alternate with each other with a repetition pitch denoted by the reference number 8 in FIG. 2.

(15) The gas-permeable wall 6 is modular, namely comprises a plurality of panels 7 assembled together to form the wall 6 itself. FIG. 2 shows a portion of a panel 7.

(16) Each of said panels 7 extends over a given angular sector of the wall 6. More precisely, each panel 7 extends in a circumferential direction over at least one pitch, namely comprises at least one rib 9 and a useful surface 10. A single panel 7 may extend in the circumferential direction over a plurality of pitches and consequently comprises a certain number of ribs 9 and useful surfaces 10.

(17) In most cases the pitch 8 is advantageously comprised between 100 and 200 mm. A single panel 7 may have a width for example of about 1 meter. The number of panels 7 needed to complete the wall 6 (i.e. to cover the wall 4) depends on the diameter of the reactor, for example in a reactor with a diameter of 3 meters the wall 6 may require 8-10 panels.

(18) During use, a gas stream fed into the cavity 11 passes into the catalytic bed through the permeable wall 6 (more precisely through the perforated sectors 10) or, vice versa, a stream flowing out from the catalytic bed is collected, through the wall 6, inside the interspace 11.

(19) The reactor also comprises means for locally securing together the gas-permeable wall 6 and said supporting wall 4, which in the example comprise threaded pins 13 engaged with locking wedges 14.

(20) The threaded pins 13 are welded to the supporting wall 4 and pass through openings 15 formed in the ribs 9. The wedges 14 are inserted in the V-shaped recesses defined by said ribs 9 on the inner side of the wall 6, that is the side facing the catalyst.

(21) The wedges 14 preferably engage said V-shaped recesses with a contact between the side surfaces which creates a slight force-fit (wedge effect). The wedges 14 are locked with suitable means, for example each wedge 14 has a hole 16 which receives the pin 13 and is then fixed by means of a nut 17.

(22) The head of the pin 13 is welded to the surface of the supporting wall 4. In this way, once the wedge 14 and the nut 17 have been positioned, the wall 6 and the associated panel 7 are secured to the supporting wall 4.

(23) For each of the ribs 9 a plurality of locking elements (i.e. pins 13 and respective wedges 14) are preferably provided, being aligned along a generatrix of the supporting wall 4.

(24) The panels 7 preferably have edges which are superimposed, for example along the ribs 9.

(25) The eyelet 15, as seen more clearly in FIG. 3, extends in an axial direction so as to allow a certain relative sliding movement of the respective panel 7 and the supporting wall 4.

(26) FIG. 2 shows the panels 7 resting on a support ring 18. Advantageously the engagement between the pairs of pins 13a and wedges 14a at lower height constitutes a locked rather than sliding engagement, so as to define a fixed constraining point for the permeable wall 6. More advantageously, a bottom strip 19 of the wall 6 is reinforced for example by folding over the metal sheet.

(27) FIG. 4 shows a variant of the invention in which the ribs 9 comprise a flat surface 20 abutting against the supporting wall 4 and the locking elements are formed by flat plates 21.

(28) The configuration with flat surface 20 is advantageous compared to a configuration with a V-shaped rib since it provides a larger space for the locking elements which may also be designed with a simpler shape, i.e. flat plates rather than wedges machined or made from folded sheet metal.

(29) FIG. 5 shows a variant of the invention in which the panels 7 have a profile in the form of an isosceles triangle. The useful surfaces 10 consequently comprise two flat surfaces 10a, 10b which are angled relative to each other.

(30) FIG. 6 shows a variant of the invention in which the panels 7 have a curvilinear profile, more advantageously in the form of a circular arc. The circular-arc profile may be preferred because it makes the best possible use of the strength of the material, i.e. it allows the panels 7 to have a minimum thickness, all the other conditions remaining the same. Moreover, for the same distance between adjacent ribs 9, the circular-arc profile offers the maximum useful surface area 10.

(31) The embodiment shown in FIG. 6 is advantageous also from the point of view of the gas-flow cross section (in the form of a semicircle) between the supporting wall 4 and the panel 7. Said gas-flow cross section represents the cross section necessary for distributing uniformly the gas over the entire height of the catalytic bed or for collecting the gas at the outlet of the said catalytic bed.

(32) The panels 7 are arranged alongside so as to form a wall 6 adjacent to the supporting wall 4 along the entire circumferential extension thereof. In some embodiments a special closing joint for the first and last panels may be provided.

(33) FIG. 7 shows an example of a closing joint for panels with V-shaped ribs of the type shown in FIG. 3.

(34) This figure shows two end panels 7 (first and last panel) and a closing joint 30 comprising two elements 31 with a V-shaped end rib 32 which is superimposed on the ribs of the panels 7. The joint 30 further comprises a support piece 33 on which the elements 31 rest and are bolted.

(35) FIG. 8 shows an example of a closing joint 40 for panels with flat bearing surfaces of the type shown in FIG. 4. The two end panels 7 terminate in flanges 41 provided with eyelets 44; said eyelets 41 are superimposed in a zone 42 where a locking plate 43 substantially similar to the plates 21 is positioned. The plate 43 has preferably two teeth 45 for preventing excessive tightening of the wall 6. Excessive tightening in fact would not allow relative sliding of the perforated wall 6 and supporting wall 4.

(36) FIGS. 9 and 10 show a further embodiment which comprises sheet-metal strips 50 arranged in the ribs 9 and designed to reinforce and protect the panels 7 against the danger of instability due to a vertical load. The addition of reinforcing elements for protection against vertical loads is appropriate if the panels are thin and/or if the catalytic bed is considerably long.

(37) It should be noted that a variant of the type shown in FIGS. 9 and 10, including reinforcements against vertical loads, is applicable in an equivalent manner to the various forms of panel all falling within the scope of the invention, such as the embodiments of FIGS. 2-6.

(38) In some embodiments the reactor does not comprise a catalytic cartridge and the gas-permeable wall 6 rests directly on the shell 2. The embodiments of FIGS. 2 to 10 are equally applicable providing that supporting wall 4 illustrated in the figures is replaced by the shell 2.

(39) The assembly procedure comprises essentially the following steps which are described with reference to FIG. 2.

(40) A first panel 7 is positioned bringing the respective rib 9 against the wall 4 and bringing the bottom edge of the panel 7 to rest on the ring 18.

(41) The threaded pins 13 are welded to the wall 4, through the openings 15. This welding operation may be advantageously performed using a capacitive-discharge welder provided with pin-welding gun which allows the head of the pin 13 to be welded to the surface of the wall 4.

(42) The locking wedges 14 are inserted and fixed with the respective nuts. In this way the panel 7 is firmly secured to the wall 4.

(43) The following panels 7 are mounted until the wall 6 around the supporting wall 4 is complete.

(44) The closing joint 30 is made for example in accordance with the scheme of FIG. 7 or another depending on the configuration of the panels 7.

(45) The aforementioned procedure may be carried out in the context of modernization of an existing reactor. In this case the panels 7 are inserted inside the reactor through an available opening, such as a manhole. In view of their small thickness, the panels may be folded and suitably bound so that they can be inserted through the manhole.