Device and method for separating a gas-solid mixture

Abstract

The invention relates to a device and method for separating a particulate gas-solid mixture, comprising / using: a substantially vertical inlet pipe (23) suitable for receiving the particulate gas-solid mixture (13); a first bend (24) of substantially 90°, connected to the lower end of the inlet pipe and having a substantially vertical upper inlet and a substantially horizontal lower outlet; a second bend (27) of substantially 90°, connected to the lower end of the first bend and having a substantially horizontal upper inlet and a substantially vertical lower outlet; a discharge pipe (25) connected to the concave side of the first bend, the projection of which in the plane of symmetry of the first bend has an angle α1 of between 5° and 85°, relative to the vertical, and the projection of which in a horizontal plane has an angle α2 of between 0° and 90° with respect to the plane of symmetry of the first bend.

Description

[0001] Device and method for separating gas-solid mixture

[0002] Technical field

[0003] The invention is in the context of catalytic cracking units. In particular, the invention relates to devices for the separation and optionally the stripping of a gas-solid mixture leaving a rising or descending gas-solid co-current fluidized bed reactor (riser or up flow reactor). The invention also relates to the use of said devices in a catalytic cracking process for the conversion of hydrocarbons.

[0004] Prior art

[0005] Fluid catalytic cracking (FCC, abbreviated for "fluid catalytic cracking" in English terminology; HSFCC, abbreviated for "high-severity fluid catalytic cracking" in English terminology) processes allow the conversion of a heavy hydrocarbon feedstock (e.g., vacuum diesel, vacuum residue, atmospheric residue, plastics, biomass), by cracking into lighter hydrocarbon fractions (e.g., gasoline, LPG or liquefied petroleum gas, as well as heavier cuts noted LCO or "Light Cycle Oil" in English terminology, and HCO or "Heavy Cycle Oil" in English terminology. The reactor used in catalytic cracking units is generally a riser or downer type reactor.

[0006] The prior art in the field of gas-solid separation at the riser or downer outlet of catalytic cracking units is very vast and we will consider the following documents as particularly relevant with regard to the present invention:

[0007] Patent EP0852963 describes a gas-solid separator with direct winding of the particles contained in a gas mixture and its use in thermal or catalytic cracking in a fluidized bed. The device applies to a riser whose upper part opens into the stripping zone, which is not the case with the present invention.

[0008] Patent FR2767715 describes a separation and stripping device for the main riser of FCC units. In the cited document, this is a riser whose upper part opens into the stripping zone. The path of the gaseous effluents shows a lateral shift since the gas reversal which takes place in chamber 2 is followed by a movement into chamber 3, as seen in Figure 3 of the cited document.

[0009] Patent US8383051 describes a gas-solid separation device which is intended for external risers, i.e. which are not at least partly contained in the stripper casing. The main flow of the gas-solid suspension is divided into two and the device comprises an impaction plate (called in English terminology "partitioning baffle" in the cited text) which makes it possible to recover the solid by abruptly reducing its speed. The device described is connected to a stripping chamber. The present invention can be considered as an improvement of the cited document.

[0010] Patent EP1017762 describes a gas-solid separation system comprising a set of separation chambers and stripping chambers arranged alternately around the riser. This system allows the following operations to be carried out simultaneously:

[0011] - separation of gas and particles in separation chambers,

[0012] - the introduction into the stripper of the bulk of the catalyst separated at the level of the separation chambers through conduits minimizing the entrainment of hydrocarbons,

[0013] - the passage of gas from the separation chambers into the stripping chambers which allow the separation between the gas and the catalyst particles to be perfected, and the said gas to be mixed with the effluents from the stripper,

[0014] - rapid evacuation of all gaseous effluents from the riser and the stripping chamber to the reactor cyclones for final separation before leaving the reactor.

[0015] Patent application FR3104467 relates to a device and a method for separating and stripping a gas mixture and solid particles comprising a plurality of separation and pre-stripping chambers distributed around a central reactor, each pre-stripping chamber comprising a peripheral wall, two substantially vertical side walls which are also the side walls of the separation chambers, a lower stripping gas inlet opening adapted to communicate with a stripping chamber, and an upper outlet opening for the gas mixture and the stripping gas adapted to communicate with a second separation stage, in which a deflector is arranged between the stripping chamber and the pre-stripping chamber and is adapted to deflect the ascending stripping gas and constrain said stripping gas to have at least one substantially horizontal movement.

[0016] Patent application FR3104469 relates to a device and a method for separating and stripping a gaseous mixture and solid particles comprising a plurality of separation and pre-stripping chambers distributed around a central reactor, each pre-stripping chamber comprising a peripheral wall, a lower outlet opening for solid particles adapted to communicate with the stripping chamber, an upper outlet opening for the gaseous mixture and stripping gas adapted to communicate with a second separation stage, and a lateral inlet opening for the stripping gas.

[0017] Summary of the invention

[0018] A first object of the present description is to provide a device and a method allowing gas-solid separation (solid particles) allowing to have a solid efficiency greater than 80% with a gas efficiency greater than 90%. A second object of the present description is to provide a device and a method allowing rapid gas-solid separation with a simple chain of two elbows. A third object of the present description is to provide a device and a method allowing to mix the gas effluents with the stripping gases while carrying out a gas-solid separation.

[0019] According to a first aspect, the present invention relates to a device for separating a particulate gas-solid mixture, comprising:

[0020] - a substantially vertical inlet pipe, adapted to receive the gas-particulate solid mixture;

[0021] - a first elbow of substantially 90°, connected to the lower end of the inlet pipe and having a substantially vertical upper inlet and a substantially horizontal lower outlet;

[0022] - a second elbow of substantially 90°, connected to the lower end of the first elbow and having a substantially horizontal upper inlet and a substantially vertical lower outlet;

[0023] - an exhaust pipe connected to the concave side of the first elbow, the projection of which in the plane of symmetry of the first elbow has an angle a1 of between 5° and 85°, preferably between 10° and 60° and preferably between 10° and 45°, relative to the vertical, and the projection of which in a horizontal plane has an angle a2 of between 0° and 90°, preferably between 10° and 80° and preferably between 15° and 75°, relative to the plane of symmetry of the first elbow.

[0024] According to one or more embodiments, the inlet pipe has a diameter D2 and a length H1, the diameter D2 being chosen to allow a gas speed of between 1 and 80 m / s, preferably between 3 and 50 m / s and preferably between 3 and 15 m / s, for a gas volume flow rate of between 0.1 m 3 / s and 170 m 3 / s, H1 being between 1*D2 and 40*D2, preferably between 1*D2 and 30*D2 and more preferably between 1*D2 and 20*D2. According to one or more embodiments, the diameter D2 is between 0.05 m and 16 m and / or the length H1 is between 0.05 m and 20 m.

[0025] According to one or more embodiments, the first elbow and the second elbow have a radius of curvature of between 1.5*D2 and 4*D2, preferably between 2*D2 and 4*D2 and more preferably between 2*D2 and 3*D2. According to one or more embodiments, the radius of curvature of the elbows is between 0.075 m and 20 m and / or the diameter of the elbows is substantially equal to D2.

[0026] According to one or more embodiments, the exhaust pipe has a diameter D3 of between 0.2*D2 and 2*D2, preferably between 0.3*D2 and 1.5*D2 and preferably between 0.5*D2 and 1.1*D2, for a gas volume flow rate of between 0.1 m 3 / s and 170 m 3 / s. According to one or more embodiments, the diameter D3 is between 0.025 m and 20 m.

[0027] According to one or more embodiments, the device comprises a return leg connected to the lower outlet of the second elbow. According to one or more embodiments, the first return leg has a diameter D4 chosen to allow a solid flow of between 10 kg / m2 / s and 400 kg / m2 / s, preferably between 20 kg / m2 / s and 350 kg / m2 / s and more preferably between 20 kg / m2 / s and 150 kg / m2 / s, for a mass flow rate of particles of between 0.002 tn / s and 8 tn / s. According to one or more embodiments, the diameter D4 is preferably between 0.1 m and 20 m.

[0028] According to one or more embodiments, the device comprises:

[0029] - a second pipe connected to the upper end of the exhaust pipe; and

[0030] - a pre-stripping chamber connected to the second pipe; the pre-stripping chamber comprising:

[0031] - a barrel, a substantially cylindrical tube with a vertical wall, having a closed upper side and an open lower side;

[0032] - a vertical outlet pipe connected to the upper side of the barrel and opening the upper side substantially along the vertical central axis of the barrel;

[0033] - a narrowing cone extending downwards the vertical wall of the barrel, in which the lower end of the narrowing cone is of smaller diameter than the diameter of the upper end of the narrowing cone, and the wall of the narrowing cone has an angle a3 of between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°, with the lower side;

[0034] - a tube arranged in the center of the narrowing cone along the vertical central axis of the barrel, the lower end of the tube being arranged below the lower end of the narrowing cone, the diameter of the tube being strictly less than the diameter of the lower end of the narrowing cone, the tube and the lower end of the narrowing cone together forming an annular space;

[0035] - a widening cone extending the tube downwards, in which the lower end of the widening cone has a diameter greater than the diameter of the upper end of the widening cone, and the wall of the widening cone has an angle a4 of between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°, with the horizontal.

[0036] According to one or more embodiments, the outlet end of the second conduit is substantially horizontal and is preferably connected to the vertical wall of the barrel in a substantially tangential manner.

[0037] According to one or more embodiments, the second conduit is connected to the upper portion of the vertical wall of the barrel and is preferably connected to the upper end of the vertical wall of the barrel.

[0038] According to one or more embodiments, the passage section of the second pipe is chosen to allow a gas speed of between 3 m / s and 50 m / s, preferably between 4 m / s and 40 m / s and preferably between 5 m / s and 30 m / s, for a gas volume flow rate of between 0.1 m 3 / s and 170 m 3 / s. According to one or more embodiments, the second pipe has a circular section with a diameter L1 or preferably a rectangular section with a height H3 and a width L1, the ratio H3 to L1 is between 1 and 20, preferably between 2 and 10 and more preferably between 2 and 7. According to one or more embodiments, the length H3 is preferably between 0.05 m and 20 m and the length L1 is between 0.01 m and 20 m.

[0039] According to one or more embodiments, the vertical outlet pipe has a diameter D8 chosen to allow a gas speed of between 1 m / s and 80 m / s, preferably between 3 m / s and 50 m / s and preferably between 3 m / s and 25 m / s, for a gas volume flow rate of between 0.11 m 3 / s and 275 m 3 / s. According to one or more embodiments, the diameter D8 is preferably between 0.05 m and 20 m.

[0040] According to one or more embodiments, the height H6, penetration length of the vertical outlet pipe into the barrel, is between 0 and 8*D8, preferably between 0 and 5*D8 and more preferably between 0 and 3*D8.

[0041] According to one or more embodiments, the barrel has a diameter D5 between (2*L1 + 1*D8) and (10*L1 + 5*D8) and preferably between (2*L1 + 1*D8) and (3*L1 + 2*D8), L1 being the width or the diameter of the second pipe.

[0042] According to one or more embodiments, the barrel has a height H4 of between 1*D5 and 10*D5, preferably between 1*D5 and 7*D5 and more preferably between 1*D5 and 3*D5.

[0043] According to one or more embodiments, the annular space has a width L2 chosen to allow a solid particle flow between 100 kg / m 2 / s and 1000 kg / m 2 / s, preferably between 200 kg / m 2 / s and 900 kg / m 2 / s and preferably between 350 kg / m 2 / s and 750 kg / m 2 / s, for a mass flow rate of solid particles between 0.002 tn / s and 8 tn / s.

[0044] According to one or more embodiments, the height H7 between the lower end of the narrowing cone and the lower end of the tube is between 0 and 20*L2, preferably between 1*L2 and 10*L2 and more preferably between 2*L2 and 8*L2. According to one or more embodiments, the length L2 is preferably between 0.01 m and 5 m.

[0045] According to one or more embodiments, the height H5 is between 1*H7 and 1.5*H4, preferably between 1*H7 and 1*H4 and more preferably between 1*H7 and 0.8*H4.

[0046] According to one or more embodiments, the diameter D7 of the lower end of the widening cone is between (2*L2 + 1*D6) and (3*L2 + 2*D6).

[0047] According to one or more embodiments, the tube has a diameter D6 chosen to allow a fluidization gas speed of between 1 m / s and 30 m / s, preferably between 2 m / s and 25 m / s and preferably between 3 m / s and 18 m / s for a gas volume flow rate of between 0.01 m 3 / s and 105 m 3 / s. According to one or more embodiments, the diameter D6 is preferably between 0.02 m and 10 m.

[0048] According to one or more embodiments, the device comprises:

[0049] - a third pipe connected to the upper end of the vertical outlet pipe; and

[0050] - at least one cyclone separator connected to the third pipe.

[0051] According to a second aspect, the present invention relates to a stripping enclosure comprising the device according to the first aspect.

[0052] According to a third aspect, the present invention relates to a catalytic cracking unit (eg FCC HS-FCC) comprising the stripping enclosure according to the second aspect.

[0053] According to a fourth aspect, the present invention relates to a method for separating a particulate gas-solid mixture using the device according to the first aspect and / or the stripping chamber according to the second aspect and / or the catalytic cracking unit according to the third aspect, comprising the following steps:

[0054] - introduce the mixture into the inlet pipe;

[0055] - separating the mixture to produce at least a portion of the particles and a gas and unseparated particles;

[0056] - extract gas and unseparated particles through the exhaust pipe;

[0057] - extract at least part of the particles towards the lower outlet of the second elbow.

[0058] According to one or more embodiments, the operating conditions of the stripping enclosure are chosen from the following conditions:

[0059] - temperature between 480°C and 730°C;

[0060] - absolute total pressure between 0.1 MPa and 0.5 MPa;

[0061] - superficial gas velocity between 0.1 m / s and 0.5 m / s;

[0062] - solid flow between 25 kg / m2 / s and 200 kg / m2 / s;

[0063] - solid volume fraction of dense bed between 0.25 and 0.6;

[0064] - residence time of the catalyst in the dense bed of the stripping chamber: between 10 seconds and 300 seconds.

[0065] Other characteristics and advantages of the invention of the aforementioned aspects will appear on reading the description below and non-limiting examples of embodiments, with reference to the figures appended and described below. List of figures

[0066] Figure 1 schematically shows a device according to the invention comprising an external riser, a so-called rapid separator, a pre-stripping chamber and a cyclonic separator.

[0067] Figure 2 schematically shows a device according to the invention comprising a downer, a so-called rapid separator, a pre-stripping chamber and a cyclonic separator.

[0068] Figure 3 schematically shows a so-called fast separator according to Figure 1.

[0069] Figure 4 schematically shows a top view of a so-called rapid separator according to Figure 3.

[0070] Figure 5 shows schematically a so-called fast separator according to Figure 2.

[0071] Figure 6 schematically shows a pre-stripping chamber according to Figures 1 and 2.

[0072] Figure 7 schematically shows a sectional view of the pre-stripping chamber according to Figure 6.

[0073] Figure 8 schematically shows a sectional view of the pre-stripping chamber connected to multi-inlets.

[0074] Figure 9 schematically shows a sectional view of a reference pre-stripping chamber.

[0075] Detailed description of the invention

[0076] Embodiments according to the foregoing aspects will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the device and method according to the present invention. However, it will be apparent to those skilled in the art that the device may be implemented without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0077] In this specification, the term "comprise" is synonymous with (means the same as) "comprise", "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Furthermore, in this specification, the terms "essentially" or "substantially" or "about" correspond to an approximation of ± 10%, preferably ± 5%, very preferably ± 1%. For example, substantially 90° corresponds to 90° ± 9°, preferably ± 4° or 5°, very preferably ± 1°. In this specification, the term "*" represents the multiplication sign. In this specification, the term "pilot unit" represents an experimental unit designed on a small scale.

[0078] In this description, the terms solid efficiency and gas efficiency are as defined below. Math 1

[0079] Math 2

[0080] The present invention relates to devices and methods used for the separation of a gas-solid (particulate) mixture (suspension) and optionally for the stripping of solid particles contained in the gas-solid mixture, the gas-solid mixture being obtained from an external riser or a downer of an FCC or HS-FCC unit. Figures 1 and 2 show the general layout of a separation and stripping device and method according to the invention in the case of an external riser 1 and a downer 20, respectively. The riser / downer is connected to a stripping enclosure 3 adapted to contain a fluidized bed located in the lower part of said stripping enclosure 3. In operation, a gas-solid mixture 13 which circulates in the external riser 1 or the downer 20 enters the stripping enclosure 3 and produces a fluidized bed, the latter being separated into a so-called dense phase 6 and a so-called dilute phase 8.In Figures 1 and 2, the interface 7 delimits the separation between the two phases. In addition, the fluidized solid in the dense phase 6 leaves the stripping enclosure 3 through the outlet conduit 19. Preferably, a fluidizing gas 16 is introduced into the stripping enclosure 3, in particular for the fluidization of the dense phase 6.

[0081] The invention relates to a device for separating and optionally stripping a gas-solid mixture, comprising: a so-called rapid separator 4; optionally a pre-stripping chamber 10; and optionally one or more cyclonic separators 12, the device being adapted to treat the gas-solid mixture entering the stripping enclosure 3. In the case of the external riser 1 of figure 1, the junction between the external riser 1 and the rapid separator 4 is made with a first pipe 2. In the case of the downer 20 of figure 2, the first pipe 2 is optional. Preferably only an end portion of the first pipe 2 and of the downer 20 enters the stripping enclosure 3. However, the first pipe 2 and the downer 20 could also be positioned mainly or even entirely inside the stripping enclosure 3.

[0082] The rapid separator 4, the pre-stripping chamber 10 and the cyclonic separator 12 are located in the dilute phase 8 of the stripping chamber 3. Preferably, the rapid separator 4 and / or the cyclonic separator 12 are provided with return legs for the separated solid descending towards (or even directly into) the dense phase 6, see first return leg 5 for the rapid separator 4 and second return leg 21 for the cyclonic separator 12 in figures 1 and 2. They can be more or less immersed in the dense phase depending on the pressure balance of the FCC or HS-FCC unit.

[0083] With reference to Figures 1 and 2, the gas-solid mixture 13 which circulates in the external riser 1 or the downer 20 enters the rapid separator 4 where a separation between the gas and the solid particles is carried out. A first portion of particles 14 is separated from the gas and descends towards the dense phase 6 by the first return leg 5. The gas and the unseparated particles 15 are then directed towards the pre-stripping chamber 10 through a second pipe 9. In the pre-stripping chamber 10, a second portion of the particles 14 is separated from the gas and falls into the dilute phase 8 to then join the dense phase 6. Advantageously, the fluidization gas 16 of the dense phase 6 enters the pre-stripping chamber 10 without re-entraining the particles 14 thanks to a device presented below.The fluidizing gas 16 as well as the gas coming from the riser and the rest of the unseparated particles 17 then go to a cyclonic separator 12 known to those skilled in the art through the third pipe 11. The implementation of a cyclonic separator is not necessarily necessary, there can also be one or more stages of cyclones. In a cyclonic separator 12, a third part of the separated particles 14 goes to the dense bed 6 through the first return leg 21, the gases 18 (and optionally the fluidizing gas 16) leave the stripping enclosure 3 through the fourth pipe 32.

[0084] Although Figures 1 and 2 show the presence of the pre-stripping chamber 10, it is understood that the presence of the pre-stripping chamber 10 is optional. The same applies to the cyclonic separator 12.

[0085] According to one or more embodiments, the external riser 1 or the downer 20 have (are suitable for):

[0086] - a gas speed of between 1 and 80 m / s, preferably between 3 and 50 m / s and more preferably between 3 and 25 m / s; and / or

[0087] - a particle flow between 10 and 2000 kg / m 2 / s, preferably between 50 and 1500 kg / m 2 / s and preferably between 100 and 1200 kg / m 2 / s.

[0088] Figures 3, 4 and 5 show the geometry of the fast separator 4 in the external riser configuration or in the downer configuration.

[0089] In the case of an external riser 1 (see figure 3), the gas-solid mixture 13 is introduced into a so-called inlet pipe 23 of the rapid separator 4 from the first pipe 2. The inlet pipe 23 is substantially vertical and is adapted for a downward gas / particle flow. Preferably, the first pipe 2 is substantially horizontal and the first pipe 2 is connected to the upper end of the inlet pipe 23 by means of a so-called connection elbow 22, for example of substantially 90°. In the case of a downer 20 (see Figure 5), the gas-solid mixture 13 is introduced directly into the upper end of the inlet pipe 23 of the rapid separator 4 from the downer 20. With reference to Figures 3 and 5, the first pipe 2 and the downer 20 as well as the connecting elbow 22 have a diameter D1, and the inlet pipe 23 is adapted for a downward gas / particle flow and has a diameter D2 and a length H1.It is understood that the connection elbow may have a diameter between D1 and D2.

[0090] At the outlet (lower end) of the inlet pipe 23, the rapid separator 4 comprises a baffle comprising a sequence of a first (pipe in the form of) elbow 24 and a second (pipe in the form of) elbow 27 together forming a zigzag path. In particular, the first elbow 24, of substantially 90°, has a substantially vertical upper inlet (connected to the inlet pipe 23) and a substantially horizontal lower outlet; and the second elbow 27, of substantially 90°, has a substantially horizontal upper inlet (connected to the first elbow 24) and a substantially vertical lower outlet. Preferably, said elbows are directly connected to each other.

[0091] With reference to figures 3, 4 and 5, a so-called exhaust pipe 25 (substantially straight) is connected (by its lower end) to the concave side of the first elbow 24 at an angle a1 relative to the vertical in the vertical plane “xz” (plane of symmetry of the first elbow 24; see figures 3 and 5) and at an angle a2 relative to the vertical plane “xz” in the horizontal plane “xy” (see figure 4). Advantageously, the sequence of the first elbow 24 and the second elbow 27 as well as the positioning of the exhaust pipe 25 allow a separation of a first part of the particles 14 and the gas (by centrifugation). The first part of the particles 14 thus separated descends into the first return leg 5 through the second elbow 27. The gas and the unseparated particles 15 exit through (the upper end of) the exhaust pipe 25 then an optional vertical pipe 26 and finally through a second pipe 9.Preferably, the second pipe 9 is substantially horizontal. With reference to Figures 3 and 5, the pipes 25 and 26 have a diameter D3 and the pipe 26 has a height H2. Furthermore, the first return leg 5 (straight vertical tube) has a diameter D4. The first return leg 5 can dip into the dense phase 6 as shown in the figures. This allows operation where the gas cannot pass through the return leg 5 and therefore forces its passage through the exhaust pipe 25. The second pipe 9 is of circular section with a diameter L1 or preferably of rectangular section with a height H3 and a width L1 (see also Figures 6, 7 and 8 described below).

[0092] According to one or more embodiments, the volume flow rate of gas (of the gas-solid mixture 13) passing through the external riser 1, the downer 20 and the inlet pipe 23, is between 0.1 m 3 / s and 170 m 3 / s; the mass flow rate of solid particles (of the gas-solid mixture 13) passing through the external riser 1, the downer 20 and the inlet pipe 23 is between 0.002 tn / s and 8 tn / s.

[0093] According to one or more embodiments, the diameter D1 is chosen to allow a gas speed of between 1 m / s and 80 m / s, preferably between 3 m / s and 50 m / s and preferably between 3 m / s and 25 m / s. According to the incoming gas volume flow range presented above, the diameter D1 is preferably between 0.05 m and 16 m.

[0094] According to one or more embodiments, the diameter D2 is chosen to allow a gas speed of between 1 m / s and 80 m / s, preferably between 3 m / s and 50 m / s and more preferably between 3 m / s and 15 m / s. According to the incoming gas volume flow range presented above, the diameter D2 is preferably between 0.05 m and 16 m.

[0095] According to one or more embodiments, H1 is between 1*D2 and 40*D2, preferably between 1*D2 and 30*D2 and more preferably between 1*D2 and 20*D2. According to the incoming gas volume flow range presented above, the length H1 is preferably between 0.05 m and 20 m.

[0096] According to one or more embodiments, the elbows have a radius of curvature between 1.5*D2 and 4*D2, preferably between 2*D2 and 4*D2 and more preferably between 2*D2 and 3*D2. According to the incoming gas volume flow range presented above, the radius of curvature of the elbows is preferably between 0.075 m and 20 m. According to one or more embodiments, the diameter of the elbows is substantially equal to D2.

[0097] According to one or more embodiments, the diameter D4 is chosen to allow a solid flow of between 10 kg / m 2 / s and 400 kg / m 2 / s, preferably between 20 kg / m 2 / s and 350 kg / m 2 / s and preferably between 20 kg / m 2 / s and 150 kg / m 2 / s. According to the incoming solid particle mass flow range presented above, the diameter D4 is preferably between 0.1 m and 20 m.

[0098] According to one or more embodiments, the angle a1 (angle between the vertical middle of the inlet pipe 23 and the middle of the exhaust pipe 25 in the “xz” plane) is between 5° and 85°, preferably between 10° and 60° and more preferably between 10° and 45°.

[0099] According to one or more embodiments, the angle a2 (angle between the vertical middle of the inlet pipe 23 and the middle of the exhaust pipe 25 in the “xy” plane) is between 0° and 90°, preferably between 10° and 80° and more preferably between 15° and 75°.

[0100] According to one or more embodiments, D3 is between 0.2*D2 and 2*D2, preferably between 0.3*D2 and 1.5*D2 and more preferably between 0.5*D2 and 1.1*D2. According to the incoming gas volume flow range presented above, the diameter D3 is preferably between 0.025 m and 20 m.

[0101] Figures 6, 7 and 8 show the geometry of the pre-stripping chamber 10 located (directly) downstream of the rapid separator 4. The gas and the unseparated particles 15 enter the pre-stripping chamber 10 through the second pipe 9. Figure 7 shows a configuration with a single pipe 9, Figure 8 shows a configuration with several (four) pipes 9, the pipes 9 being connected to one or more (four) rapid separators 4. In the pre-stripping chamber 10, the gas and the unseparated particles 15 enter a barrel 27, a substantially vertical cylindrical tube whose upper side (substantially circular base) is closed (solid) and whose lower side (substantially circular base) is open.The barrel has a diameter D5 and a height H4 in order to initiate a centrifugal separation between the gas and the particles, the particles descending along the vertical wall of the barrel 27 and the gas exiting the barrel 27 through a vertical outlet pipe 31 arranged in the upper part along the vertical central axis of the barrel 27. To do this, the second pipe 9 is preferably connected substantially tangentially with the vertical wall of the barrel 27 as shown in Figure 7. One or more tangential pipes 9 may be implemented as shown in Figures 7 and 8. Preferably, the outlet end of the second pipe 9 is substantially horizontal. Preferably, the second pipe 9 is connected to the upper part (egthe upper half, preferably the upper third, or even the upper quarter) of the vertical wall of the barrel 27, very preferably the second pipe 9 is connected to the upper end of the vertical wall of the barrel 27. The vertical outlet pipe 31 has a diameter D8 and penetrates a height H6 inside the barrel 27. A narrowing cone 28 (conical tube) is placed below the barrel 27 to extend downwards the vertical wall of the barrel 27, the upper end of the narrowing cone 28 having a diameter D5 and the lower end of the narrowing cone 28 having a diameter less than D5, the barrel 27 and the narrowing cone 28 having the same vertical axis of symmetry. In addition, the wall of the narrowing cone 28 has an angle a3 with the plane formed by the lower side (substantially horizontal plane) and a height H8.

[0102] Referring to Figure 6, a tube 29 (straight) is arranged in the center of the narrowing cone 28 along the vertical central axis of the barrel 27 and extends below the narrowing cone (28) to a lower end of the tube 29, the lower end of the tube 29 being arranged at a height H7 below the lower end of the narrowing cone 28, and the upper end of the tube 29 being arranged at a height H5 below the lower end of the vertical outlet pipe 31. Furthermore, the tube 29 has a diameter D6 strictly less than the diameter of the lower end of the narrowing cone 28, the lower end of the narrowing cone 28 having a diameter (1*D6 + 2*L2).A widening cone 30 (conical tube) is arranged at the lower end of the tube 29, the upper end of the widening cone 30 being of diameter D6 and the lower end of the widening cone 30 being of diameter D7, D7 being strictly greater than D6. Furthermore, the widening cone 30 has an angle a4 with the horizontal (or the plane formed by the lower open side of the tube 29) and a height H9.

[0103] The operating principle of the pre-stripping chamber 10 is as follows. The gas and the unseparated particles 15 enter tangentially into the barrel 27 causing a centrifugal separation of the particles. The second part of the particles 14 then falls towards the narrowing cone 28 and joins the diluted phase 8 of the stripping chamber 3 through an annular space of width L2. L2 is the length between the lower end of the narrowing cone 28 and the tube 29. Furthermore, the fluidizing gas 16 enters the pre-stripping chamber 10 through (from the inside) the widening cone 30 and is then directed upwards through the tube 29. At the outlet of the tube 29, the fluidizing gas 16 joins the part of the gas and the unseparated particles 15 to form a gas mixture 17 exiting the pre-stripping chamber through the vertical outlet pipe 31.The gas mixture 17 can then exit (directly) from the stripping chamber 3 or be sent to one or more cyclonic separators 12 by means of the third pipe 11. Advantageously, the implementation of the widening cone 30 and the tube 29 allow the fluidization gas 16 to enter the pre-stripping chamber 10 without re-entraining the second part of the particles 14.

[0104] According to one or more embodiments, the volume flow rate of the stripping gas 16 is between 0.01 m 3 / s and 105 m 3 / s. According to one or more embodiments, the sum of the volume flow rate of gas (of the gas-solid mixture 13) and of the stripping gas 16 passing through the barrel 27 and entering the vertical outlet pipe 31 is between 0.11 m 3 / s and 275 m 3 / s.

[0105] According to one or more embodiments, the passage section of the second pipe 9 (eg H3*L1) is chosen to allow a gas speed of between 3 m / s and 50 m / s, preferably between 4 m / s and 40 m / s and preferably between 5 m / s and 30 m / s. According to one or more embodiments, the ratio H3 to L1 is between 1 and 20, preferably between 2 and 10 and preferably between 2 and 7. According to the incoming gas volume flow range presented above, the length H3 is preferably between 0.05 m and 20 m and the length L1 is between 0.01 m and 20 m.

[0106] According to one or more embodiments, the diameter D8 is chosen to allow a gas speed of between 1 m / s and 80 m / s, preferably between 3 m / s and 50 m / s and more preferably between 3 m / s and 25 m / s. According to the incoming gas volume flow range presented above, the diameter D8 is preferably between 0.05 m and 20 m.

[0107] According to one or more embodiments, the diameter D5 of the barrel 27 is between (2*L1 + 1*D8) and (10*L1 + 5*D8) and preferably between (2*L1 + 1*D8) and (3*L1 + 2*D8).

[0108] According to one or more embodiments, the height H4 of the barrel 27 is between 1*D5 and 10*D5, preferably between 1*D5 and 7*D5 and more preferably between 1*D5 and 3*D5.

[0109] According to one or more embodiments, L2 is chosen to allow an annular space between the lower end of the narrowing cone 28 and the tube 30 to obtain a solid particle flow between 100 kg / m 2 / s and 1000 kg / m 2 / s, preferably between 200 kg / m 2 / s and 900 kg / m 2 / s and preferably between 350 kg / m 2 / s and 750 kg / m 2 / s. According to the incoming solid flow range presented above, the length L2 is preferably between 0.01 m and 5 m.

[0110] According to one or more embodiments, the angle a3 between the horizontal and the wall of the narrowing cone 28 is between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°. The height H8 results from the angle a3 and the lengths D6 and L2. According to one or more embodiments, the diameter D6 is chosen to allow a fluidization gas velocity of between 1 m / s and 30 m / s, preferably between 2 m / s and 25 m / s and more preferably between 3 m / s and 18 m / s. According to the incoming gas volume flow range presented above, the diameter D6 is preferably between 0.02 m and 10 m.

[0111] According to one or more embodiments, the height H7 between the lower end of the narrowing cone 28 and the lower end of the tube 29 is between 0 and 20*L2, preferably between 1*L2 and 10*L2 and more preferably between 2*L2 and 8*L2.

[0112] According to one or more embodiments, the height H5 is between 1*H7 and 1.5*H4, preferably between 1*H7 and 1*H4 and more preferably between 1*H7 and 0.8*H4.

[0113] According to one or more embodiments, the height H6 (penetration length of the vertical outlet pipe 31 in the barrel 27) is between 0 and 8*D8, preferably between 0 and 5*D8 and more preferably between 0 and 3*D8.

[0114] According to one or more embodiments, the angle a4 between the horizontal and the wall of the widening cone 30 is between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°. According to one or more embodiments, the diameter D7 of the lower end of the widening cone 30 is between (2*L2 + 1*D6) and (3*L2 + 2*D6). The height H9 results from the angle a4 and the diameter D7.

[0115] According to one or more embodiments, the operating conditions of the stripping enclosure 3 are chosen from the following conditions:

[0116] - temperature between 480°C and 730°C;

[0117] - absolute total pressure between 0.1 MPa and 0.5 MPa;

[0118] - superficial gas velocity between 0.1 m / s and 0.5 m / s;

[0119] - solid flow between 25 kg / m2 / s and 200 kg / m2 / s;

[0120] - solid volume fraction of dense bed between 0.25 and 0.6;

[0121] - residence time of the catalyst in the dense bed of stripping chamber 3: between 10 seconds and 300 seconds.

[0122] Examples

[0123] As a first example, we compare a reference FCC pilot unit comprising a stripping chamber comprising two cyclonic separators (counter-example), and an FCC pilot unit according to the invention comprising a stripping chamber 3 comprising a rapid separator 4, a pre-stripping chamber 10 and two cyclonic separators 12 (example according to the invention).

[0124] The main dimensions of the pilot units are shown below:

[0125] Riser diameter: 1.5 cm - Stripper diameter: 10 cm

[0126] - D1 = 1.5 cm

[0127] - D2 = 2.1 cm

[0128] - D3 = 2.1 cm

[0129] - D4 = 2.1 cm

[0130] - a1=70°

[0131] - a2=30°

[0132] - 1-11 = 30 cm

[0133] - 1-12 = 10 cm

[0134] - H3 = 3 cm

[0135] - L1 = 1 cm

[0136] - L2 = 0.4 cm

[0137] - H4 = 8cm

[0138] - H5 = 7.5 cm

[0139] - H6 = 0 cm

[0140] - H7 = 3 cm

[0141] - H8 = 9 cm

[0142] - H9 = 3.5 cm

[0143] - a3=80°

[0144] - a4=70°

[0145] - D5 = 4 cm

[0146] - D6 = 1.7 cm

[0147] - D7 = 2.9 cm

[0148] - D8 = 1.4 cm.

[0149] In this first example, the FCC pilot units are in adiabatic mode, the feedstock is a vacuum diesel fuel which is brought into contact with an equilibrium FCC catalyst. Table 1 below shows a comparison between the reference FCC pilot unit and the FCC pilot unit according to the invention.

[0150] Table 1

[0151] From Table 1, we see that the pilot unit according to the invention allows to reduce the residence time (measured by a Residence Time Determination technique, or DTS) and also reduces coking (lower Acoke). Advantageously, the temperature at the regenerator is reduced and the C / O ratio is increased. In addition, a better conversion is obtained (+3.2% relative) with less dry gas (-23.5% relative), a better propylene yield (+2.3% relative), a better olefinicity of the C3 cut (+5% relative) and a better yield of light gasoline (+7.9% relative).

[0152] In particular, the rapid separator 4 makes it possible to reduce the gas residence time and improve the performance of the unit as shown above. In addition, the pre-stripping chamber 10 makes it possible to remix the stripping gases with the riser effluents while performing a gas-solid separation.

[0153] As a second example and with reference to Figure 9, we compare a diagram of a reference pre-stripping chamber 40 and a pre-stripping chamber 10 according to the invention. In particular, Figure 9 shows a diagram of a reference pre-stripping chamber 40 comprising two lateral inlets 41 through which the mixture 15 of gaseous effluents and solid particles enter. The stripping gas 16 enters from the bottom through the lower inlet 42 and the gaseous mixture 17, a mixture of the flows 15 and 16, exits from the top through the upper outlet 43.

[0154] The gas and solid efficiency of the reference pre-stripping chamber 40 are known. The solid efficiency of the pre-stripping chamber 10 according to the invention is measured on pilot size with:

[0155] - L1 = 1 cm

[0156] - H3 = 3 cm

[0157] - H4 = 8cm

[0158] - H5 = 7.5 cm

[0159] - H6 = 0 cm

[0160] - H7 = 3 cm

[0161] - H8 = 9 cm

[0162] - H9 = 3.5 cm

[0163] - a3=80°

[0164] - a4=70°

[0165] - D5 = 4 cm

[0166] - D6 = 1.7 cm

[0167] - D7 = 2.9 cm

[0168] - D8 = 1.4 cm. The table below compares the gas and solid efficiencies of the reference pre-stripping chamber 40 with the pre-stripping chamber 10 according to the invention.

[0169] Table 2

[0170] The solid efficiency of the new invention is superior while maintaining the same gas efficiency.

Claims

Claims 1. Device for separating a particulate gas-solid mixture, comprising: - a substantially vertical inlet pipe (23), adapted to receive the particulate gas-solid mixture (13); - a first elbow (24) of substantially 90°, connected to the lower end of the inlet pipe (23) and having a substantially vertical upper inlet and a substantially horizontal lower outlet; - a second elbow (27) of substantially 90°, connected to the lower end of the first elbow (24) and having a substantially horizontal upper inlet and a substantially vertical lower outlet; - an exhaust pipe (25) connected to the concave side of the first elbow (24) whose projection in the plane of symmetry of the first elbow (24) has an angle a1 of between 5° and 85°, preferably between 10° and 60° and preferably between 10° and 45°, relative to the vertical, and whose projection in a horizontal plane has an angle a2 of between 0° and 90°, preferably between 10° and 80° and preferably between 15° and 75°, relative to the plane of symmetry of the first elbow (24); - a return leg (5) connected to the lower outlet of the second elbow (27), in which the first elbow (24) and the second elbow (27) have a radius of curvature between 1.5*D2 and 4*D2, preferably between 2*D2 and 4*D2 and more preferably between 2*D2 and 3*D2, the diameter D2 being between 0.05 m and 16 m.

2. Device according to claim 1, in which the inlet pipe (23) has a diameter D2 and a length H1, the diameter D2 being chosen to allow a gas speed of between 1 and 80 m / s, preferably between 3 and 50 m / s and preferably between 3 and 15 m / s, for a gas volume flow rate of between 0.1 m 3 / s and 170 m 3 / s, H 1 being between 1 *D2 and 40*D2, preferably between 1*D2 and 30*D2 and more preferably between 1*D2 and 20*D2.

3. Device according to claim 1 or claim 2, in which the exhaust pipe (25) has a diameter D3 of between 0.2*D2 and 2*D2, preferably between 0.3*D2 and 1.5*D2 and preferably between 0.5*D2 and 1.1*D2, for a gas volume flow rate of between 0.1 m 3 / s and 170 m 3 / s.

4. Device according to claim 1, in which the return leg (5) has a diameter D4 chosen to allow a solid flow of between 10 kg / m2 / s and 400 kg / m2 / s, preferably between 20 kg / m2 / s and 350 kg / m2 / s and preferably between 20 kg / m2 / s and 150 kg / m2 / s, for a mass flow rate of particles of between 0.002 tn / s and 8 tn / s, the diameter D4 being between 0.1 m and 20 m.

5. Device according to any one of the preceding claims, comprising: - a second pipe (9) connected to the upper end of the exhaust pipe (25); and - a pre-stripping chamber (10) connected to the second pipe (9); the pre-stripping chamber (10) comprising: - a barrel (27), a substantially cylindrical tube with a vertical wall, having a closed upper side and an open lower side; - a vertical outlet pipe (31) connected to the upper side of the barrel (27) and opening the upper side substantially along the vertical central axis of the barrel (27); - a narrowing cone (28) extending downwards the vertical wall of the barrel (27), wherein the lower end of the narrowing cone (28) is of smaller diameter than the diameter of the upper end of the narrowing cone (28), and the wall of the narrowing cone (28) has an angle a3 of between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°, with the lower side; - a tube (29) arranged in the center of the narrowing cone (28) along the vertical central axis of the barrel (27), the lower end of the tube (29) being arranged below the lower end of the narrowing cone (28), the diameter of the tube (29) being strictly less than the diameter of the lower end of the narrowing cone (28), the tube (29) and the lower end of the narrowing cone (28) together forming an annular space; - a widening cone (30) extending downwards the tube (29), in which the lower end of the widening cone (30) has a diameter greater than the diameter of the upper end of the widening cone (30), and the wall of the widening cone (30) has an angle a4 of between 45° and 88°, preferably between 50° and 85° and more preferably between 60° and 80°, with the horizontal.

6. Device according to claim 5, wherein the outlet end of the second conduit (9) is substantially horizontal and is preferably connected to the vertical wall of the barrel (27) in a substantially tangential manner.

7. Device according to claim 5 or claim 6, wherein the second conduit (9) is connected to the upper part of the vertical wall of the barrel (27) and is preferably connected to the upper end of the vertical wall of the barrel (27).

8. Device according to any one of claims 5 to 7, comprising: - a third pipe (11) connected to the upper end of the vertical outlet pipe (31); and - at least one cyclonic separator (12) connected to the third pipe (11).

9. Stripping enclosure comprising the device according to any one of claims 1 to 8.

10. Catalytic cracking unit comprising the stripping chamber according to claim 9.

11. Method for separating a particulate gas-solid mixture using the device according to any one of claims 1 to 8, comprising the following steps: - introduce the mixture (13) into the inlet pipe (23); - separating the mixture (13) to produce at least a portion of the particles (14) and a gas and unseparated particles (15); - extracting the gas and unseparated particles (15) through the exhaust pipe (25); - extract at least part of the particles (14) towards the lower outlet of the second elbow

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