Gas injection element for a fluid catalytic cracking unit and gas distribution system equipped with this injection element

Abstract

A gas injection element (10) for a system for distributing a gas inside a chamber of a fluid catalytic cracking unit. This injection member comprises a passage (14) extending entirely therethrough, andan inner ceramic member (20) having an inner surface (22) that entirely delimits the through-passage (14); anda hollow metal sleeve (30), inside which at least a portion of the inner member (20) is received, the sleeve (30) and the inner member (20) respectively having an inner surface (32) and an outer surface (24) with matching shapes allowing the inner member (20) to move relative to the sleeve (30) in a direction parallel to an axis (X) of the passage (14), the outer (32) and inner surfaces (24) being provided with fastening elements (26, 36) that engage to reversibly fasten the sleeve and the inner member.

Claims

1. A gas injection element for a system for distributing gas into a chamber of a fluid catalytic cracking unit, said injection element comprising a passage passing right through said injection element, characterized in that said injection element comprises: an internal element made of ceramic material of which an internal surface defines said through-passage over the entire length thereof, said internal element having an external surface on the opposite side to said internal surface, a hollow metal sleeve having an internal surface, inside which sleeve there is housed at least part of the internal element, the internal surface of the sleeve facing the external surface of the internal element, the internal surface of the sleeve and the external surface of the internal element being of complementing shapes allowing the internal element to move with respect to the sleeve in a direction parallel to an axis (X) of the through-passage, said internal surface of the sleeve and external surface of the internal element being provided with fixing elements that collaborate to fix the sleeve and the internal element reversibly, wherein the fixing elements comprise lugs or notches collaborating respectively with grooves or ribs of a suitable shape to allow the sleeve and the internal element to move between a fixed state and a freed state following movements in translation in a direction parallel to the axis of revolution and in rotation about the axis of revolution.

2. The gas injection element as claimed in claim 1, characterized in that the external surface of the internal element and the internal surface of the sleeve are surfaces of revolution, notably cylinders of revolution, having an axis of revolution coincident with or parallel to the axis (X) of the through-passage.

3. The gas injection element as claimed in claim 1, characterized in that the sleeve is of cylindrical shape.

4. The gas injection element as claimed in claim 1, characterized in that the internal element has, at one of its ends, a flange bearing, in the fixed state, against one end of the sleeve in the direction of the axis of the through-passage.

5. The gas injection element as claimed in claim 1, characterized in that the ceramic material is chosen from silicon carbide SiC, boron carbide B.sub.4C, silicon nitride Si.sub.3N.sub.4, aluminum nitride AlN, boron nitride BN, alumina Al.sub.2O.sub.3, or mixtures of these.

6. The gas injection element as claimed in claim 1 characterized in that the ceramic material comprises a ceramic matrix chosen from silicon carbide SiC, boron carbide B.sub.4C, silicon nitride Si.sub.3N.sub.4, aluminum nitride AlN, boron nitride BN, alumina Al.sub.2O.sub.3 or mixtures of these, into which ceramic matrix there are incorporated fibers chosen from carbon fibers and ceramic fibers, the ceramic fibers being chosen for example from crystalline alumina fibers, mullite fibers, crystalline or amorphous silicon carbide fibers, zirconium fibers, silica-alumina fibers, or mixtures of these.

7. A distribution system for distributing gas inside a chamber of a fluid catalytic cracking unit, said distribution system comprising a support wall pierced with at least one orifice and defining at least part of a cavity, the support wall having a first face intended to be in contact with a gas contained in this cavity, and a second face on the opposite side to the first face, characterized in that it comprises at least one injection element as claimed in claim 1, the injection element being secured to the support wall, at the orifice, so that gas originating from the cavity can circulate through the support wall toward the second face thereof via the passage of the internal element secured to the sleeve, only the sleeve being secured to the support wall.

8. The gas distribution system as claimed in claim 7, characterized in that one end of the sleeve is secured to the support wall in such a way as not to project from the second face of said support wall.

9. The gas distribution system as claimed in claim 7, characterized in that one end of the sleeve is inserted into the orifice.

Description

(1) The invention is now described with reference to the attached non-limiting drawings in which:

(2) FIG. 1 illustrates a partial schematic depiction in cross section of a chamber comprising a gas distribution system according to one embodiment;

(3) FIG. 2 illustrates a partial schematic depiction in cross section of an injection element according to one embodiment;

(4) FIG. 3 depicts a view of FIG. 2 in cross section on A-A.

(5) FIG. 1 partially depicts a chamber 100 that forms part of a fluid catalytic cracking FCC unit not depicted in its entirety. The chamber depicted here is a chamber of a regenerator, in which coke deposited on the catalyst coming from a reactor of the FCC unit (not depicted) is burnt off.

(6) The catalyst in the chamber 100 forms a fluidized bed 102.

(7) A distribution system 1 allows air, and therefore the oxygen needed for burning the coke, to be injected into this fluidized catalytic bed 102.

(8) This distribution system 1 comprises a support wall, in this instance a perforated plate 11, occupying the entirety of a section of the chamber 100, and supporting the fluidized bed 102. This plate thus, with the end walls of the chamber, defines an air cavity 103. A pipe 104 opening onto this cavity 103 is able to supply pressurized air.

(9) The plate thus comprises a first face 105 in contact with the air of the cavity 103 and a second face 106 in contact with the fluidized bed 102.

(10) The perforated plate 11 here is a steel plate 11a. It may have a refractory coating 11b made of composite material (depicted in FIG. 2) on the side of the second face 106. This refractory coating is obtained for example by pouring concrete onto a steel mesh not depicted, for example in the form of a honeycomb comprising a plurality of hexagonal mesh cells joined to one another along their sides (a hex mesh), or the like.

(11) Mounted on each orifice 13 of the plate 11 is a gas injection element 10, in this instance an air injection nozzle.

(12) This injection element 10 is described with reference to FIGS. 2 and 3. It comprises a passage 14 passing right through it, of axis X. The injection element 10 is thus secured to the support wall 11 in such a way that gas originating from the cavity 103 can circulate through the support wall 11 toward the second face 106 thereof via the through-passage 14.

(13) This injection element 10 further comprises: an internal element 20 made of ceramic material, a hollow metal sleeve 30, inside which at least part of the internal element 20 is housed.

(14) The internal element 20 comprises an internal surface 22, which defines the through-passage 14 over the entire length thereof, and an external surface 24. As visible in FIGS. 2 and 3, this internal surface 22 and this external surface 24 are on opposite sides and extend parallel to the axis X of the through-passage 14.

(15) The sleeve 30 comprises an internal surface 32 and an external surface 34. This internal surface 32 and this external surface 34 are also on opposite sides and extend parallel to the axis X of the through-passage 14.

(16) The internal surface 32 of the sleeve 30 and the external surface 24 of the internal element 20 have complementing shapes allowing the internal element 20 to move with respect to the sleeve 30 in a direction parallel to the axis X of the through-passage. This internal surface 32 of the sleeve and this external surface 24 of the internal element are also provided with fixing elements that collaborate to fix the sleeve 30 and the internal element 20 reversibly.

(17) In general, whatever the embodiment and notably whatever the shape of the support wall 11, this internal surface 32 of the sleeve and this external surface 24 of the internal element are configured to allow a relative movement of the sleeve 30 and of the internal element 20 between a fixed state of the sleeve and of the internal element, in which these elements, are secured to one another, and a freed state of these elements in which they can be separated from one another. For preference, the transition from one state to the other is obtained by a movement of the internal element 20, the sleeve 30 remaining fixed.

(18) In the example depicted, the external surface 24 of the internal element 20 and the internal surface 32 of the sleeve 30 are surfaces of revolution, in this instance cylinders of revolution, having an axis of revolution coincident with or parallel to, in this instance coincident with, the axis X of the through-passage.

(19) In this example, it will be noted that the internal element 20 is cylindrical over a large proportion of its length (just one of its ends 21 having a narrowing), the sleeve 30 being entirely cylindrical.

(20) It will also be noted that the sleeve 30 surrounds the internal element 20 over just a part of its length. However, the invention is not limited to a particular length and shape of the sleeve 30 and of the internal element 20, provided that they can be secured to/detached from one another.

(21) Thus, in general, when the internal element 20 is housed inside the sleeve 30, the external surface 24 of the internal element 20 faces the internal surface 32 of the sleeve 30.

(22) In the example depicted, the fixing elements that secure the internal element 20 to the sleeve 30 comprise lugs or notches collaborating respectively with grooves or ribs of a suitable shape to allow the sleeve 30 and the internal element 20 to move between the fixed state and the freed state following movements in translation in a direction parallel to the axis of revolution X and in rotation about the axis of revolution X.

(23) More specifically, in this example, the sleeve 30 has lugs 36 which project from its internal surface 32 perpendicular to the axis of revolution X, toward the latter (radially). These lugs 36 collaborate with grooves 26 formed in the external surface 24 of the internal element 20. These grooves 26 are, for example, L-shaped, with one part (visible in FIG. 3) extending parallel to the axis X from one end 21 of the internal element 20, allowing the internal element 20 to be inserted inside the sleeve 30 in a translational movement of axis X, the end of the groove 26 turning at right angles (FIG. 2) so as to allow the internal element 20 to be rotated with respect to the sleeve 30 and locked. FIG. 3 depicts a view in transverse section of the internal element and of the sleeve, before the rotation of the internal element 20, whereas FIG. 2 is a depiction after rotation. Thus, in the first relative position depicted in FIG. 3, the internal element 20 can be extracted from/inserted into the sleeve 30 by a translational movement along the axis X, the lugs 36 sliding along the first part of the grooves 26 parallel to the axis X, inside these grooves 26. In the second relative position depicted in FIG. 2, the lugs 36 are in the second part of the grooves 26 which part extends in a plane perpendicular to the axis X: the only possible movement between the sleeve 30 and the internal element 20 is a rotation about X. In other words, the cross section depicted in FIG. 3 is a section on A-A depicted in FIG. 2, but the internal element 20 depicted in FIG. 3 is in a different position from that depicted in FIG. 2. It will thus be appreciated that, from the position depicted in FIG. 2, it is possible to pivot the internal element 20 with respect to the axis X in order to bring it into the position depicted in FIG. 3, allowing it to be extracted from the sleeve 30 by a translational movement parallel to the axis X.

(24) The invention is not limited to this particular embodiment: the lugs 36 could form part of the internal element 20 and the grooves 26 be produced on the sleeve 30. It might also be possible to envision replacing the lugs with notches collaborating not now with grooves but with ribs parallel to the axis X and the length of which is chosen so that the rotation of the parts relative to one another allows the end of the ribs to bear against the unnotched periphery of the other part. Neither is the invention limited to a particular number of ribs/grooves and notches/lugs, it also being possible for these various embodiments to be combined.

(25) It will be noted that, in the example depicted, one end 33 of the sleeve 30 is secured to the support wall 11 in such a way as not to project from the second face 106 of said support.

(26) In the example, this end 31 is inserted into the orifice 13 in the support wall 11 and fixed thereto by a welded seam 35. The external surface 34 of the sleeve in this instance is welded to the support wall 11.

(27) Furthermore, the internal element 20 has an end 23 provided with a flange 25, which here bears in the direction of the axis X against the end 33 of the sleeve 30 when the two elements are in the fixed state. In the example, this flange 25 comes against the coating 12 and lies flush therewith (see FIG. 2). The invention is not limited to this particular embodiment; the flange could be larger and bear against the second face 106. The internal element could equally have no flange 25.

(28) It will be noted that, in the fixed state, only the sleeve 30 is secured to the support wall 11, so that the internal element 20 can easily be replaced, through a suitable movement.

(29) The gas injection element has been described with reference to a system for distributing air in a regenerator of an FCC unit. The invention is not limited to this embodiment; the gas distribution system could equally be a system for distributing steam in a stripping zone of a reactor of an FCC unit, or any other gas or steam injection element of an FCC unit.