Ceramic orifice chamber for fluid catalytic cracking unit

Abstract

The invention relates to an orifice chamber designed to expand a gas, in particular intended for a fluid catalytic cracking unit, said orifice chamber comprising the following elements: a chamber having an axis (X), an inlet duct that opens into the chamber, an outlet duct located on the opposite side from the inlet duct following said axis (X), and a plurality of internal plates positioned crosswise to the axis (X) inside the chamber at a distance from one another along the axis (X), each internal plate being provided with a plurality of through-orifices, characterized in that at least the plurality of internal plates is made of a ceramic material.

Claims

1. An orifice chamber designed to expand a gas, in particular intended for a fluid catalytic cracking unit, said orifice chamber comprising the following elements: a chamber having an axis (X), an inlet duct that opens into the chamber, an outlet duct located on the opposite side from the inlet duct following said axis (X), and a plurality of internal plates positioned crosswise to the axis (X) inside the chamber at a distance from one another along the axis (X), each internal plate being provided with a plurality of through-orifices, characterized in that at least the plurality of internal plates is made of a ceramic material and the ceramic material comprises a ceramic matrix selected from the group consisting of 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, and mixtures thereof, in which carbon fibres or ceramic fibres are incorporated in the ceramic matrix.

2. The orifice chamber according to claim 1, characterized in that the chamber and/or each duct is made of metal or made of ceramic material.

3. The orifice chamber according to claim 1, characterized in that the ceramic fibres comprise crystalline alumina fibres, mullite fibres, crystalline or amorphous silicon carbide fibres, zirconia fibres, silica-alumina fibres, or mixtures thereof.

4. The orifice chamber according to claim 1, characterized in that the ceramic material is a sintered ceramic material.

5. The orifice chamber according to claim 1, characterized in that the ceramic material is a Ceramic Matrix Composite (CMC).

6. The orifice chamber according to claim 1, characterized in that each internal plate is formed from one part made of ceramic material.

7. The orifice chamber according to claim 1, characterized in that the elements are separate elements made of ceramic material that are assembled together, a separate element being made of one part or being made of several portions assembled together.

8. The orifice chamber according to claim 1, 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.

9. The orifice chamber according to claim 1, characterized in that the chamber is made of metal and in that the internal plates made of ceramic material are assembled to the metal chamber by fastening means capable of absorbing a difference in expansion between the metal of the chamber and the ceramic material of an internal plate.

10. The orifice chamber according to claim 1, characterized in that the chamber is made of ceramic material and has a reinforcing outer covering in mesh form.

11. A system for recovering power from the flue gases exiting a regenerator of a fluid catalytic cracking unit comprising at least one orifice chamber according to claim 1.

12. A catalytic cracking unit comprising at least one orifice chamber according to claim 1.

13. The catalytic cracking unit according to claim 12 further comprising the system for recovering power according to claim 11.

14. A method of preparing an orifice chamber made of Ceramic Matrix Composite (CMC), 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 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.

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 system for recovering power from the flue gases of an FCC unit,

(3) FIG. 2 is a schematic representation, in axial cross section, of an orifice chamber,

(4) FIG. 3 is an enlargement of FIG. 2,

(5) FIGS. 4a and 4b are axial cross-sectional views of the ends of two assembled parts. The assembled parts are separated in FIG. 4b for greater clarity.

(6) In the present description, the terms upstream and downstream refer to the direction of circulation of the flue gases.

(7) FIG. 1 represents a system 10 for recovering power from the flue gases of an FCC unit. This system is of a type known per se.

(8) Represented in FIG. 1 are a regenerator 1 that supplies a reactor 2 with regenerated catalyst, in which reactor catalytic cracking reactions of a hydrocarbon feedstock take place.

(9) In the regenerator 1, the coke, deposited on the catalyst particles during catalytic cracking reactions, is burnt off using air injected at the base of the regenerator 1 through a line 3. The flue gases G, after separation of the particles through one or two cyclone stages (not represented) located in the upper portion of the regenerator, are discharged through a line 4 to the recovery system 10.

(10) In the example represented, this recovery system 10 comprises a third stage separation 12 located downstream of the regenerator 1. This third stage separation 12, which comprises one or more cyclones (not represented), thus collects the flue gases G directly exiting the regenerator 1.

(11) The recovery system 10 additionally comprises, from upstream to downstream, starting from the third stage separation 12, a flue gas expansion train 14 comprising: a control valve 16, an orifice chamber 18.

(12) The above expansion train 14 may be used as a bypass of a power recovery train 20, which is also located downstream of the third stage separation 12, directly connected to the latter.

(13) This power recovery train 20 comprises: a control valve 22, an expander 24, an air blower 26, which provides the regenerator 1 with the air needed for the combustion,

(14) a generator 28, optionally a start-up steam turbine 30.

(15) Such a power recovery train is known and will not be explained further.

(16) Finally, the flue gases exiting the orifice chamber 18 and/or the expander 24 are then successively treated in: a heat recovery device 32 in order to produce a flow of steam V, such as for example a CO boiler or a heat exchanger, an electrostatic precipitator 34,
before being discharged through a stack 36.

(17) On the diagram represented in FIG. 1, the expansion train 14 essentially makes it possible to control the pressure of the regenerator 1 when the power recovery train 20 is not operating or when the flue gas flow rate reaches the maximum capacity of the expander 24.

(18) The power recovery system represented also comprises a 4.sup.th stage separation 38 of particles, downstream of the third stage separation 12, and an injection nozzle 40. The solid catalyst particles are recovered by the line 39.

(19) In a variant that is not represented, the recovery train 20 may be absent: the third stage separation 12 may then be omitted, as well as the fourth stage separation 38 and the injection nozzle 40.

(20) The invention is not limited to the flue gas power recovery system described and relates to any known system for recovering power from the flue gases of an FCC unit.

(21) FIG. 2 schematically represents, in longitudinal cross section, an orifice chamber 18 which comprises: a chamber 181 having an axis (X), an inlet duct 182 that opens into the chamber 181, an outlet duct 183 located on the opposite side from the inlet duct 182 following said axis (X), and a plurality of internal plates 184 positioned crosswise to the axis X inside the chamber at a distance from one another along the axis X, each internal plate being provided with a plurality of through-orifices 185. These orifices 185 are designed to provide a reduction of the pressure of the flow circulating through the orifice chamber 18.

(22) In general, as represented in the example, the chamber 181 is formed of several sections 181a, 181b, 181c interlocked in twos via conical end portions 181d, 181e. Two adjacent sections are represented in detail in FIG. 3. In general, a chamber 181 has a cylindrical shape, for example a diameter of the order of 50 cm to 1 m for a height of approximately 5 meters. The orifices 185 of the plates are the order of 10 cm in diameter.

(23) According to the invention, at least the internal plates 184 are made of ceramic material, preferably of silicon carbide SiC. They are 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 internal plates are 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.

(24) These internal plates 184 may be fastened to a fastening face 186, which is present in the form of an annular support (or flange) in the example, firmly attached to be internal wall 181i of the chamber. This fastening face or annular support 186 extends crosswise to the axis X.

(25) If the chamber is made of metal, this annular support is then also made of metal and an internal plate 184 made of ceramic material may be assembled to the annular support 186 by at least two metal tabs 187 firmly attached to the annular support 186 and shaped to bear against the edge 184a of an internal plate 184 in order to keep this edge 184a bearing against the annular support 186 of the chamber. In this case, the internal plate 184 has dimensions slightly smaller than the internal dimensions of the chamber in order to allow the installation of the metal tabs 187. As a variant, these metal tabs 187 could be welded directly to the internal wall 181i of the chamber 181.

(26) As a variant, the chamber 181, in other words each section 181a, 181b, 181c of the chamber in the example represented, may also be made of ceramic material. In this case, the internal plates 184 may be assembled to the fastening face 186 by brazing or welding, a seal being optionally inserted between the fastening face 186 and the internal plate 184.

(27) If the inlet duct 182 and outlet duct 183 are also made of ceramic material, they may be produced from one part with the chamber or a section of the chamber.

(28) The inlet duct 182 and outlet duct 183 made of ceramic material may also be parts separate from the chamber and be assembled thereto. An inlet duct 182 (or an outlet duct) may for example be interlocked with the chamber 181 as represented schematically in FIG. 4a by interlocking of conical end portions of complementary shape, or by screwing of their ends (FIG. 4b), or else welded or brazed (not represented). Similarly, the sections of the chamber 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.

(29) The invention is not limited to the examples described. In particular, the chamber 181 may be produced from a single part, made of metal or made of ceramic material, and not from assembled sections. The various embodiments described, and in particular the various methods of assembly, may in addition be combined.