Termination device of a reactor of a fluid catalytic cracking unit

Abstract

The invention relates to a termination device of a tubular reactor comprising at least one separation element adapted for the separation of solid particles and gaseous effluents and at least one coupling element that is part of an end of said tubular reactor, said separation element being connected to said coupling element, characterized in that each element of the termination device is made of ceramic material. The invention also relates to a tubular reactor, having a vertical or substantially vertical axis, of a fluid catalytic cracking unit equipped with a termination device according to the invention and to a corresponding fluid catalytic cracking unit.

Claims

1. A termination device of a tubular reactor comprising: at least one separation element adapted for the separation of solid particles and gaseous effluents and at least one coupling element that is part of an end of the tubular reactor, the separation element being connected to the coupling element, characterized in that each element of the termination device is made of ceramic material and the ceramic material comprises a ceramic matrix selected from silicon carbide SiC, boron carbide B.sub.4C, silicon nitride Si.sub.3N.sub.4, aluminium nitride AlN, boron nitride BN, alumina Al.sub.2O.sub.3, or mixtures thereof, incorporated in which ceramic matrix are carbon fibres or ceramic fibres.

2. The termination device according to claim 1, characterized in that the ceramic fibres are selected from the group consisting of crystalline alumina fibres, mullite fibres, crystalline or amorphous silicon carbide fibres, zirconia fibres, silica-alumina fibres, and mixtures thereof.

3. The termination device according to claim 1, characterized in that the ceramic material is a sintered ceramic material.

4. The termination device according to claim 1, characterized in that the ceramic material is a Ceramic Matrix Composite (CMC).

5. The termination device according to claim 1, characterized in that the elements form one and the same part made of ceramic material.

6. The termination device according to claim 1, characterized in that the elements are separate elements made of ceramic material that are assembled together, an element being made of one part or of several portions assembled together.

7. The termination device according to claim 6, characterized in that the elements and/or the portions are assembled by welding or brazing or in that elements to be assembled and/or portions to be assembled have ends shaped in order to be assembled by interlocking or screwing.

8. The termination device according to claim 1, characterized in that the coupling element comprises a bent pipe, in particular a rounded bent pipe, or a straight pipe.

9. The termination device according to claim 1, characterized in that the separation element is selected from the group consisting of a cyclone, a circulation separation element and a ballistic separation element.

10. A tubular reactor having a vertical or substantially vertical axis, of a fluid catalytic cracking unit equipped with at least one termination device according to claim 1.

11. The tubular reactor according to claim 10 made of metal, characterized in that the reactor is connected to the termination device by fastening means suitable for absorbing a difference in expansion between the metal of the reactor and the ceramic material of the termination device.

12. The tubular reactor according to claim 10, characterized in that the tubular reactor is made of ceramic material and is connected to the termination device by welding, brazing, screwing or interlocking.

13. A catalytic cracking unit comprising at least one tubular reactor according to claim 10.

14. A method of preparation of a termination device of a tubular reactor, wherein each element of the termination device is made of Ceramic Matrix Composite (CMC), the method comprising: 1) shaping a fibrous ceramic material 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 element 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.

Description

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

(2) FIG. 1 is a schematic representation of a termination device according to a first embodiment;

(3) FIG. 2 is a schematic representation of a termination device according to a second embodiment;

(4) FIG. 3 is a schematic representation of a termination device according to a third embodiment;

(5) FIG. 4 is a cross-sectional schematic representation of a termination device according to a fourth embodiment;

(6) FIGS. 4a and 4b are transverse cross-sectional views of two types of cyclone at their inlet duct,

(7) FIG. 5 is a schematic representation of an end portion of a reactor of an FCC unit according to the prior art,

(8) FIGS. 6a and 6b are axial cross-sectional views of the ends of two assembled parts. The assembled parts are separated in FIG. 6b for greater clarity,

(9) FIG. 7 shows an example of assembling a cyclone to the end portion of a reactor, in particular a metal reactor, FIG. 7a showing a detail from this FIG. 7.

(10) The termination device according to the invention is made of ceramic material, preferably silicon carbide SiC. It is for example formed by injection moulding or extrusion. Injection moulding or extrusion are conventionally carried out using ceramic powders or precursors of ceramics with a binder. According to another manufacturing method, the ceramic termination device is formed by compression and heating of a ceramic powder, it being possible for the compression to be maintained during the heating step, the heating step being a step of sintering the ceramic powder. This technique is particularly well suited to the manufacture of solid elements made of silicon carbide according to the invention. The ceramic powder used optionally comprises ceramic fibres in order to increase the mechanical strength of the parts produced. The ceramic fibres, when they are present, generally represent from 0.1% to 10% by weight of the part produced.

(11) This termination device may be arranged according to any one of the termination devices known in the prior art.

(12) Some of these termination devices are described with reference to FIGS. 1 to 4. The invention is not however limited to these embodiments.

(13) FIG. 1 represents a ballistic-type termination device 10 of a tubular reactor 1 positioned vertically. The termination device 10 comprises a separation element 11 and a coupling element 12. The separation element 11 comprises a horizontal pipe 13, one end 13a of which is coupled to the coupling element 12 and the other end 13b of which is closed perpendicular to the axis 13c of the pipe 13. The end 13b additionally has an opening 14 pointed downwards and comprising a wall 14a which is tangent with respect to the sidewall of the pipe 13 and parallel to the axis 13c of the latter. The coupling element 12 forms the upper portion of the reactor 1. It is formed from a bent pipe, in particular a pipe bent at a right angle, the bent portion of which is rounded. A first end 12a is coupled to the separation element 11, the other end 12b being coupled to the reactor 1. The mixture of gaseous hydrocarbons and of catalyst particles circulates according to an upward flow in the reactor 1 and enters through the end 13a into the separation element 11, substantially parallel to the axis 13c. The catalyst particles projected against the closed end 13b lose their velocity and then fall by gravity out of the separation element 11 via the opening 14 whilst the gases exit via the top of this opening 14. This type of termination device thus comprises a coupling element comprising a rounded bent pipe and a ballistic-type separation element. In this example, the reactor 1 may be made of metal or equally made of ceramic material. If it is made of metal, it may be assembled to the termination device with means similar to those described with reference to FIG. 7. If it is made of ceramic, it may be assembled to the termination device by welding, brazing, or else by screwing or interlocking, in a manner similar to the assemblies represented in FIGS. 6a and 6b.

(14) Other reactor termination devices exist that have in particular more complex configurations but that provide a better separation efficiency. FIG. 2 thus represents a termination device 20 which comprises a separation element 21 and a coupling element 12 identical to that described with reference to FIG. 1. The separation element 21 comprises a pipe 22 bent at 90, a horizontal portion 22a of which is coupled to the end 12a of the coupling element 12 and the vertical portion 22b of which is pointed downwards for the outlet of the particles. Two gas discharge ducts 23, 24 positioned vertically emerge from either side of a chamber 22c of the termination device 20. This chamber 22c is located under the horizontal portion 22a, in communication with the vertical portion 22b and is shaped in order to direct the incoming gas following a circular or substantially circular trajectory to the ducts 23, 24. The mixture of gaseous hydrocarbons and of catalyst particles circulates according to an upward flow in the reactor 1 and enters the separation element 21 via the horizontal portion 22a before coming back into contact against the wall of the vertical portion 22b: the particles fall by gravity in this vertical portion 22b, whilst the gases follow a circular or substantially circular trajectory before exiting in the upper portion through the vertical ducts 24, 23 via the internal chamber 22c. This type of termination device is sometimes referred to as a quarter turn separator. This type of termination device thus comprises a coupling element comprising a rounded bent pipe and a fluid circulation separation element.

(15) In the same way as in the preceding example, the reactor 1 may be made of metal or equally made of ceramic material.

(16) FIG. 3 represents another termination device 30 which comprises a separation element 31 and a coupling element 32. The coupling element 32 is a straight duct positioned vertically in the continuation of the reactor 1. The upper end 32a of the coupling element opens into two separation chambers 33 that are symmetrical about the axis 1c of the reactor and of the coupling element 32. Each separation chamber 33 has a rounded concave wall 34, the concavity of which is pointed downwards. Each separation chamber 33, also referred to as volute chamber in the present application, opens into a vertical discharge duct 35 that is pointed downwards, tangent to the concave wall 34. A vertical gas discharge duct 36 is coupled horizontally to each separation chamber 33, at the centre thereof. The mixture of gaseous hydrocarbons and of catalyst particles circulates according to an upward flow in the reactor 1, enters the separation element 31, is sent to the separation chambers 33 and impacts against their concave walls 34. Under the effect of gravity, the slowed-down catalyst particles fall and are discharged through the ducts 35. The gas is discharged in the upper portion through the ducts 36. Document EP 0 332 277 A2 describes a termination device of this type with internal recirculation of the gases, documents EP 0 852 963 B1 and U.S. Pat. No. 7,429,363 B2 describe other termination devices of this type, but without internal recirculation of the gases. This type of termination device thus comprises a coupling element comprising a straight pipe and a circulation separation element comprising one or two volute chambers. In the same way as in the preceding examples, the reactor 1 may be made of metal or equally made of ceramic material.

(17) FIG. 4 represents a termination device 40 comprising a separation element 41 and a coupling element 12. This coupling element 12 is similar to that represented in FIGS. 1 and 2. The separation element 41 is a cyclone which comprises a separation chamber 101, an inlet duct 102 that opens into the chamber 101, a gas outlet duct 103 located in the upper portion of the chamber 101 and a particle outlet duct 104 located in the lower portion of the chamber 101. The separation chamber 101, generally referred to as the body of the cyclone, is often cylindrical, as represented, or sometimes cylindroconical. In the example represented, the separation chamber 101 comprises a cylindrical upper portion 101a and a conical lower portion 101b.

(18) The lower end of smaller diameter of this conical lower portion 101b is connected to the particle outlet duct 104, which is in the form of a tube extending in the axis of symmetry X of the separation chamber 101. This tube is often referred to as a dip-leg or else leg.

(19) The inlet duct 102 receiving the gas/particle mixture, sometimes also referred to as suction eye or bell mouth, is formed of a tube positioned so as to impart a circular movement to the incoming mixture. Thus, the inlet duct 102 may either be tangential with respect to the separation chamber 101, as represented schematically in FIG. 4a, or be substantially tangential and form a volute, as represented in FIG. 4b.

(20) Under the effect of this movement, the catalyst particles fall into the conical lower portion 101b of the separation chamber 101 before being discharged through the particle outlet duct 104. The gas itself exits at the upper end of the cyclone via the gas outlet duct 103, also referred to as a stack. A dust catcher 105 may be positioned between the conical lower portion 101b of the separation chamber 101 and the particle outlet duct 104.

(21) The circulation of the gas inside the cyclone is represented by the arrows visible in FIG. 4.

(22) The separation element 41 may be made from one or more parts made of ceramic material.

(23) For example, the separation chamber 101 and the particle outlet duct 104 may be separate parts, it being possible for the inlet duct 102 and the gas outlet duct 103 to be made from one part with the separation chamber 101.

(24) The elements 101 and 104 may then be interlocked, as represented schematically in FIG. 6a by interlocking of conical end portions of complementary shape, or by screwing of their ends (FIG. 6b), or else welded or brazed (not represented). Similarly, the cylindrical upper portion 101a and the conical lower portion 101b of the separation chamber 101 may be separate portions that are assembled, it being possible for this assembling to be carried out as described above, by assembling cylindrical or conical sections, or else by assembling parts resembling bricks by interlocking and/or welding/brazing.

(25) Assembly operations similar to those described with reference to FIGS. 6a, 6b may be carried out in order to assemble a separation element and a coupling element within the meaning of the invention and/or a termination device according to the invention and a ceramic tubular reactor, irrespective of their configuration.

(26) The coupling element 12 of the termination device 40 is connected directly to the tubular reactor 1, as represented schematically in FIG. 7. When this tubular reactor 1 is made of metal, its free end 1a has a fastening face 1b, firmly attached to which are at least two metal tabs 1d shaped in order to elastically bear against an edge 12c of the coupling element 12 in order to keep this edge 12c bearing against the fastening face 1b of the reactor (FIG. 7a). This edge 12c may be located at the end 12b of the coupling element 12. For a simple production, the edge 12c and the fastening face 1b may extend over the entire periphery of the assembled portions, such as for example flanges.

(27) According to one embodiment that is not represented, the invention is also wholly applicable to a termination device of RS2 type as disclosed in EP 1 017 762 or U.S. Pat. No. 6,296,812, the content of which is incorporated here by way of reference.