Element for Injecting Fuel into a Regenerator of a Fluid Catalytic Cracking Unit

Abstract

An injection element (10) for a system for injecting fuel into a regenerator of a fluid catalytic cracking unit, said injection element defining a flow passage (12) and being arranged so as to be able to be fastened to an orifice passing through the regenerator so that one end of the flow passage (12) is connected to a duct for supplying the injection system with fuel and the other end of the flow passage opens inside the regenerator, characterized in that said injection element is made of ceramic material.

Claims

1.-11. (canceled)

12. An injection element for an injection system for injecting fuel into a regenerator of a fluid catalytic cracking unit, the injection element comprising: a flow passage and being arranged so as to be able to be firmly attached to an orifice passing through the regenerator so that one end of the flow passage is connected to a duct for supplying the injection system with fuel and the other end of this flow passage opens inside the regenerator, characterized in that the injection element is made of ceramic material comprising a ceramic matrix and carbon and/or ceramic fibres incorporated into this ceramic matrix.

13. The injection element according to claim 12, in which the ceramic material comprises silicon carbide SiC, preferably in a majority amount.

14. The injection element according to claim 12, in which the ceramic material is a Ceramic Matrix Composite (CMC).

15. An injection system for injecting fuel into a regenerator of a fluid catalytic cracking unit, the system comprising at least one injection element according to claim 12, and at least one fuel supply duct, in which the at least one injection element is arranged so that one end of the fuel injection flow passage is connected to the duct.

16. The injection system according to claim 15, in which, for at least one injection element, the injection system comprises a support sleeve inside which the injection element extends, this support sleeve being intended to be positioned through a wall of the regenerator, the injection element being arranged so as to be firmly attached to this support sleeve.

17. The injection system according to claim 15, in which, for at least one injection element, the injection system comprises a device for fastening the injection element to the support sleeve, the fastening device being capable of absorbing a difference in expansion between the material of the support sleeve and the ceramic material of the injection element.

18. The injection system according to claim 15, in which, for at least one injection element, the fastening device comprises at least one pressing element capable of exerting a force on this injection element in order to press this injection element against the support sleeve.

19. The injection system according to claim 18, in which the pressing element comprises a tab welded via one end to the support sleeve and the other end of which is capable of exerting an elastic bearing force on the injection element when the injection element is installed inside the support sleeve.

20. The process for manufacturing a fuel injection element for a regenerator of a catalytic cracking unit, so that the fuel injection element defines a flow passage for the fuel, one end of which is intended to be connected to a fuel supply duct, and the other end of which is intended to open inside the regenerator, the process being characterized in that the injection element is made of ceramic material comprising a ceramic matrix and carbon and/or ceramic fibres incorporated into this ceramic matrix, the process comprising: 1) shaping a fibrous ceramic material eventually over a supporting material that could be removed without excessive effort, in order to obtain a fibrous shape that can be assimilated to the backbone of the final device to be obtained, in the presence of a first resin, 2) coating the shape obtained at step (1) with finely divided ceramic powder and at least a second resin, in the presence of finely divided carbon powder, to obtain a coated shape, 3) repeat steps (1) and (2), 4) heating the coated shape of step (2) or (3) under vacuum and/or under inert atmosphere in order to transform the resins of step (1), (2) and (3) into a carbon-rich structure, essentially deprived of other elements to obtain a carbon-rich coated shape, 5) introducing a gas within the carbon-rich coated shape of step (4) under conditions efficient to transform the carbon-rich structure into carbide containing carbon-rich structure, 6) removing the supporting material of step (1), when present, wherein carbon fibers are present at least at step (1), (2) and/or (3) within the fibrous ceramic material, within the finely divided ceramic powder, within the finely divided carbon powder, and/or within the first and/or second resin.

21. The manufacturing process according to claim 20, comprising a step of sintering silicon carbide SiC particles.

Description

[0085] The invention will be better understood with reference to the figures, which show exemplary embodiments of the invention.

[0086] FIG. 1 shows an example of a fuel injection system according to one embodiment of the invention, shown on a regenerator wall.

[0087] FIGS. 2A, 2B and 2C are cross-sectional views of three embodiments of a fuel injection element, when installed in a support sleeve.

[0088] Identical references may be used from one figure to the next to denote elements that are identical in their shape or in their function.

[0089] With reference to FIG. 1, the system 1 comprises a fuel injection element 10, for example an injection nozzle, shown on a wall 2 of a chamber, here a regenerator, and connected to a fuel supply duct 11.

[0090] The wall 2 is in general metallic and covered with an anti-erosion coating 3 of concrete type on the face thereof inside the regenerator.

[0091] The injection element 10 is connected to the fuel supply duct 11 by a flow control device 4. Here it is a three-way valve that makes it possible to connect the injection element to the fuel supply duct 11 or to a purge circuit supplied with air (not represented).

[0092] The system 1 also comprises a support sleeve 5, passing right through the wall 2. The support sleeve 5 supports the flow control device 4. It also receives the injection element 10, as represented.

[0093] The system 1 is intended to be installed in a regenerator of a fluid catalytic cracking (FCC) unit, of which only the wall 2 is represented, and serves to provide fuel, for example gas oil or heavy fuel oil, to the inside of this regenerator. The combustion of this fuel may make it possible to increase the temperature inside the regenerator, and thus to promote the combustion of coke deposited on catalyst resulting from a reactor of the FCC unit and to improve the thermal balance of the unit when there is not enough coke formed during the cracking reaction of a feedstock.

[0094] The injection nozzle 10 is made of ceramic, for example made of silicon carbide SiC.

[0095] This nozzle 10 is obtained by sintering a silicon carbide powder below its melting point.

[0096] Advantageously, ceramic fibres may be added during the preparation of the ceramic part, whether it is prepared by powder sintering or by a wet route, the wet route being that commonly used for making ceramic or porcelain crockery articles, or construction materials, for example clay bricks.

[0097] Preferably, from 0.1% to 10% by weight of ceramic fibres are added during the step of manufacturing the nozzle 10.

[0098] Such a nozzle, made of solid ceramic, has a relatively low manufacturing cost and does not result in a significant additional cost with respect to a steel that has undergone a surface treatment, for example a nitridation or a boration, or a special steel having an improved abrasion resistance.

[0099] The injection nozzle 10 defines a flow passage 12 in which fuel, for example heavy fuel oil or gas oil, is intended to circulate from the duct 11 to the inside of the regenerator, along the arrow 13.

[0100] The support sleeve 5 is made of steel having an improved abrasion resistance.

[0101] This support sleeve 5 defines an orifice 6, into which a large portion of the injection nozzle 10 is introduced. As seen in FIG. 1, the end of the nozzle 10 opening into the regenerator juts out from the support sleeve 5, which itself juts out from the wall 2 of the regenerator, inside the latter. For example, the support sleeve 5 may jut out by around 300 mm on the inside of the regenerator, the distance measured from the surface of the coating 3, and the nozzle 10 may jut out by 25 mm from the end of the support sleeve 5.

[0102] Pressing elements 14 (particular embodiments of which are described with reference to FIGS. 2A, 2B and 2C), here steel tabs welded to the support sleeve 5, at its end, make it possible to exert a pressing force on a bearing surface 15 of a flange 16 of the injection nozzle 10.

[0103] Thus, the other side of the flange 16 is pressed against the perimeter of the edge of the orifice 6.

[0104] If temperature variations lead to a variation in the dimensions of this orifice 6, the fastening of the injection nozzle 10 thus remains stable despite the possible expansion of the support sleeve 5 when the temperature varies.

[0105] In FIGS. 2A, 2B and 2C the same elements are denoted by the same numerical references.

[0106] FIG. 2A is a cross-sectional view of an example of a nozzle 10 according to a first embodiment of the invention.

[0107] This nozzle 10 defines a duct 12 for the flow passage of the fuel along the arrow 19, this fuel is intended to be ignited in the regenerator in order to increase the temperature inside the generator and thus promote the regeneration of the catalyst.

[0108] This nozzle 10 is made of silicon carbide and comprises a flange 16 that comes to rest on the edges of an orifice 6 of the support sleeve 5.

[0109] The nozzle 10 has a cylindrical general shape, as does the support sleeve 5 in this embodiment.

[0110] The diameter of the nozzle 10 is smaller than the diameter of the orifice 6, so that the expansion of the support sleeve 5 does not lead to a fracture of the injection nozzle 10.

[0111] Two tabs 14 are welded to the support sleeve 5, each tab 14 comprising an end 21 intended to exert an elastic bearing force on the flange 16.

[0112] Each end 21 comprises a flat side 22 in order to avoid regions of excessively high stresses on the flange 16 of the nozzle 10.

[0113] In the embodiment from FIG. 2B, the pressing elements comprise screws 17 passing through the flange 16 and screwed into the support sleeve 5. Each screw 17 has a head 18 against which the end of a helical spring 20 surrounding the shaft of the screw bears, the other end of this spring 20 bearing against the flange 16. The springs 20 thus make it possible to press the flange 16 against the support sleeve 5.

[0114] In the embodiment from FIG. 2C, the flange 16 on the nozzle 10 is clamped between a plate 21 formed in the extension of the support sleeve 5 and a plate 22 formed in the extension of the flow control device 4. The sleeve 5 is coated with an insulating mantle 23, itself protected by a protective casing 24 (which are also visible in FIG. 1).

[0115] The nozzle 10 is kept clamped between the plates 21 and 22 with the aid of screws 18, the tightening force of which is adjusted with the aid of springs 20. In this embodiment, the fastening means are positioned on a portion of the nozzle located outside of the regenerator.

[0116] In the embodiments from FIGS. 1, 2A and 2B, the fastening means are positioned on a portion of the nozzle located inside of the regenerator. They could however be located, as for the embodiment from FIG. 2C, on a portion located outside of the regenerator.

[0117] The invention may make it possible to design nozzles 10 with greater freedom of design as regards the shape in so far as it is less necessary than in the prior art to take into account the problem of erosion by the catalyst.

[0118] In particular, a shape could be provided that makes it possible to optimize the injection of fuel, which may make it possible to improve the combustion quality, and therefore to further preserve the catalyst, which may be beneficial for the environment.

[0119] In addition, the maintenance operations, capable of imposing shutdowns and of limiting catalytic cracking, may be carried out less frequently than in the prior art.

[0120] Finally, this type of injection system may prove more reliable than in the prior art and therefore may make it possible to limit the risk of unscheduled catalytic cracking shutdown.