Mixing chamber for a gas-solid co-current downflow fluidised-bed reactor

Abstract

The invention relates to a device and a process for gas-solid co-current downflow fluidised-bed catalytic cracking comprising / using: a pipeline (1) suitable for carrying a downflow (4) of catalyst particles; a mixing chamber (2) connected to and fed by the pipeline with catalyst particles and comprising an inner wall, at least one first injector (5) of hydrocarbon feed (6) and a central bulk part (12) defining an annular zone (13) through which the catalyst particles pass through the mixing chamber; and a gas-solid co-current downflow fluidised bed reactor (3) fed by the mixing chamber with a mixture comprising catalyst particles and hydrocarbon feed, wherein the central bulk part comprises at least one internal element (11) arranged under the at least one first injector and being suitable for distributing the mixture towards the wall of the mixing chamber.

Description

[0001] Mixing chamber for a descending gas-solid co-current fluidized bed reactor.

[0002] Technical field

[0003] The invention relates to the field of refining and petrochemistry and to processes and units for the chemical transformation of petroleum products, in particular hydrocarbon cuts, by Fluid Catalytic Cracking (FCC) for the production of light olefins (i.e., olefins comprising between 2 and 4 carbon atoms), and more particularly ethylene and propylene, and also aromatics (e.g. BTX), and more particularly paraxylene.

[0004] Prior art

[0005] The invention is part of the improvement of the design of the established flow zone of downward gas-solid co-current fluidized bed reactors ("downer" or "down flow reactor" according to English terminology), hereinafter called downward flow reactors, used for example for high severity catalytic cracking (HS-FCC).

[0006] Ethylene, Propylene, Butene, Butadiene and aromatics such as Benzene, Toluene and Xylene (BTX) represent the basic products for the petrochemical industry. These products are generally obtained by catalytic reforming and / or thermal cracking (steam cracking) of hydrocarbons such as naphtha, kerosene or diesel. These compounds are also obtained by fluidized catalytic cracking (FCC) of hydrocarbons, such as a Vacuum Gas Oil (VGO) and / or a residue (under vacuum or atmospheric) from the distillation of hydrocarbons and / or naphtha, diesel, and complete crudes.

[0007] The high severity catalytic cracking (HS-FCC) process aims to increase propylene and ethylene yields through high temperature reaction conditions, very short contact times (eg ~1 s), high ratios between the mass flow rate C of catalyst and the mass flow rate O of feedstock (C / O).

[0008] The disadvantages associated with a conventional FCC reactor with a rising gas-solid co-current fluidized bed (riser) such as back-mixing and the accumulation of catalyst near the wall, resulting in overcracking of hydrocarbons and excessive formation of coke, hydrogen, methane and ethane, do not allow the production of olefins to be promoted under high severity conditions.

[0009] To overcome these drawbacks, the HS-FCC process uses a downflow reactor, where the catalyst and feedstock are moved under gravity with a flow approaching that of a plug-type flow. The downward gas-solid flow in a reactor avoids backmixing and overcracking of products while the use of high C / O ratios ensures the predominance of catalytic reactions. The high temperature favors the formation of reaction intermediates such as light olefins while a controlled and short contact time avoids side reactions that are responsible for the consumption of such intermediates.

[0010] On the other hand, the downward gas-solid flow presents several major technological challenges, one of which is the flow in the mixing chamber. Indeed, the initial mixing between catalyst and feed determines the vaporization of hydrocarbons and the gas-solid contact throughout the downflow reactor. The initial mixing is generally carried out in a fraction of a second with, for a typical HS-FCC, a flow rate of the order of 400 to 700 t / h of feed and 7000 to 21000 t / h of catalyst, which requires efficient technology to have a mixing chamber that approaches a perfectly stirred zone.

[0011] Patent FR 2 753 453 B1 describes a downward flow cracking reactor comprising a zone for bringing the hydrocarbons into contact with the catalyst, and consisting of: a mixing chamber of maximum section S2, placed in communication with means for supplying regenerated catalyst via an upper orifice defining a catalyst passage section S1; and a reaction zone of maximum section S4, placed in communication with the mixing chamber via an intermediate orifice of section S3, in which reactor the ratios S2 / S1 and S2 / S3 are between 1.5 and 8. Patent FR 2 753 453 B1 also describes a spacer piece arranged at the lower end of the catalyst conduit supplying the mixing chamber, the spacer piece defining an upper annular orifice of the mixing chamber.

[0012] Patent application US 2022 / 0016589 A1 describes a downflow reactor whose feed zone comprises an elongated spacer piece on which helical blades are positioned.

[0013] US Patents 10,889,768 B2 and US Patents 10,767,117 B2 describe systems and processes for producing petrochemical products (e.g. ethylene and other olefins), from hydrocarbon feedstocks (e.g. crude oil), in high severity fluid catalytic cracking (HS-FCC) units.

[0014] Summary of the invention

[0015] In the context described above, a first object of the present invention is to overcome the problems of the prior art and to provide a device for fluidized bed catalytic cracking with descending gas-solid cocurrent with homogeneous catalyst flow, i.e., in which the solid concentration in the cross-section of the reactor is substantially uniform. Indeed, the device according to the invention makes it possible to obtain an improved catalyst dispersion between the central zone and the annular zone (i.e., in the proximity of the wall) of the descending gas-solid cocurrent reactor.

[0016] According to a first aspect, the aforementioned objects, as well as other advantages, are obtained by a device for descending gas-solid co-current fluidized bed catalytic cracking comprising, from top to bottom: a pipe adapted to transport a descending flow of catalyst particles; a mixing chamber connected to the pipe and adapted to be fed by the pipe in descending flow, the mixing chamber comprising an internal wall, at least one first hydrocarbon feed injector and a central spacer defining an annular zone through which the catalyst particles pass through the mixing chamber; and a descending gas-solid co-current fluidized bed reactor connected to the mixing chamber and adapted to be fed by the mixing chamber with a mixture comprising catalyst particles and hydrocarbon feed, device in which the mixing chamber comprises at least one internal (egobstacle, deflector) arranged on and preferably around the central space-consuming part and arranged under the at least one first injector and being adapted to distribute the mixture towards the wall of the mixing chamber.

[0017] Advantageously, the internal allows the concentration of catalyst particles to be homogenized.

[0018] According to one or more embodiments, the at least one internal is adapted to reduce the passage section of the annular zone by 1% to 35%.

[0019] According to one or more embodiments, the at least one internal is adapted to prevent the accumulation of catalyst particles on said internal.

[0020] According to one or more embodiments, the at least one internal adapted element comprises an upper surface sloping outwardly.

[0021] According to one or more embodiments, the oblique upper surface of the at least one internal is straight, convex and / or concave.

[0022] According to one or more embodiments, the oblique upper surface of the at least one internal part forms an angle p of between 10° and 80°, relative to the horizontal. According to one or more embodiments, the at least one internal part is arranged on the central space-saving part at an axial distance from the first hydrocarbon charge injectors of between 0*H3 and 1*H3, H3 being the height of the at least one internal part.

[0023] According to one or more embodiments, the at least one internal is a plurality of internals positioned discontinuously on the central spacer piece.

[0024] According to one or more embodiments, the internals are shaped like a prism, cylinder, pyramid, cone, and / or truncated cone.

[0025] According to one or more embodiments, the device comprises at least one row of internals arranged at a predetermined height on the central space-consuming part.

[0026] According to one or more embodiments, the perimeter of the central space-consuming room wall occupied by the row of internals is between 10% and 100%.

[0027] According to one or more embodiments, the row of internals comprises between 1 and 16 internals.

[0028] According to one or more embodiments, the at least one internal member is annular in shape, and is continuously positioned on and around the central bulkhead.

[0029] According to one or more embodiments, the device comprises between 1 and 6 rows of discontinuous internals and / or between 1 and 12 annular-shaped internals arranged at a predetermined height on the central space-saving part.

[0030] According to a second aspect, the aforementioned objects, as well as other advantages, are obtained by a method for fluidized bed catalytic cracking with descending gas-solid co-current comprising the following steps: transporting a descending flow of catalyst particles in a conduit; feeding a mixing chamber via the conduit with the descending flow, the mixing chamber comprising an inner wall, at least a first hydrocarbon feed injector and a central spacer defining an annular zone through which the catalyst particles pass through the mixing chamber; feeding a descending gas-solid co-current fluidized bed reactor via the mixing chamber with a mixture comprising catalyst particles and hydrocarbon feed;and at least partially cracking the hydrocarbon feedstock in the presence of the catalyst particles in the descending gas-solid co-current fluidized bed reactor, to produce an effluent comprising at least partially coked catalyst and gaseous cracking products, wherein the mixing chamber comprises at least one internal disposed below the at least one first injector and being adapted to distribute the mixture toward the mixing chamber wall.;

[0031] 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.

[0032] List of figures

[0033] Figure 1 shows an FCC device according to one or more embodiments of the present invention comprising a central spacer provided with internals for homogenizing the catalyst flow.

[0034] Figure 2 shows a top view of an FCC device according to one or more embodiments of the present invention comprising a truncated cone-shaped mixing chamber provided with an internal continuously disposed around the central spacer.

[0035] Figure 3 shows a top view of an FCC device according to one or more embodiments of the present invention comprising a truncated cone-shaped mixing chamber provided with internals arranged discontinuously around the central spacer.

[0036] Figure 4 shows a 3D view of an FCC device according to one or more embodiments of the present invention comprising an internal continuously disposed around the central bulkhead and a plurality of obstacles on the wall of the mixing chamber.

[0037] Figure 5 shows cross-sectional views of the mass fraction of the catalyst in an FCC device according to the invention A as shown in Figure 4, and in a reference FCC device B.

[0038] Detailed description of the invention

[0039] 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.

[0040] 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%.

[0041] The invention relates to a fluidized bed catalytic cracking device and method for the chemical transformation of petroleum products (FCC), used for example for high severity catalytic cracking (HS-FCC).

[0042] An FCC unit typically processes a heavy cut from the vacuum distillation unit such as vacuum gas oil or vacuum residue, or atmospheric residue, alone or in a mixture. An FCC unit can also process lighter cuts such as gasoline or diesel cuts, alone or in a mixture. It is also possible to process a mixture of light and heavy cuts, or a complete crude. In order to increase propylene and ethylene yields by using high-severity reaction conditions (high temperature, very short contact times, high C / O ratios between the catalyst flow C and the feed O flow), catalytic cracking devices and processes typically use a downflow reactor (hereinafter referred to as a downflow reactor).

[0043] However, downward gas-solid flow presents several technological challenges, including achieving homogeneous flow and mixing in the steady-flow section of the downflow reactor.

[0044] In order to overcome these drawbacks, improvements to the downflow reactor technology described in patent FR 2 753 453 B1 have been identified, to address the challenge presented above through a specific arrangement of hydrocarbon feedstock injectors, and optionally diluent injectors, to improve the contact between the catalyst and the hydrocarbons in the mixing chamber.

[0045] The device according to the invention

[0046] Referring to Figure 1, the device for fluidized bed catalytic cracking with descending gas-solid co-current comprising, from top to bottom: a pipe 1 (substantially vertical); a mixing chamber 2; and a descending flow reactor 3 (substantially vertical).

[0047] Line 1 is adapted to supply mixing chamber 2 with solid catalyst (particles). Line 1 mainly transports solid, as well as a fluidization gas entrained by the descending solid. Line 1 has a flow like a feed column ("standpipe" according to English terminology) well known to those skilled in the art.

[0048] The mixing chamber 2 is connected to the conduit 1, comprises a side / vertical wall defining a central / vertical axis Z, and is adapted to feed the downflow reactor 3 with a mixture comprising catalyst particles, a hydrocarbon feedstock and optionally a diluent.

[0049] The downflow reactor 3 is connected to the mixing chamber 2 and is adapted to at least partially crack the hydrocarbon feedstock in the presence of the catalyst particles to produce an effluent comprising at least partially coked catalyst and gaseous cracking products, and optionally unconverted vaporized feedstock.

[0050] Specifically, with reference to Figure 1, the pipe 1 feeds the mixing chamber 2 with a descending flow 4 of (hot) catalyst particles, the mixing chamber 2 comprising one or more first injectors 5 of hydrocarbon feedstock 6. According to one or more embodiments, the first injector(s) 5 is adapted to inject diluent (e.g. water vapor) with the feedstock. According to one or more embodiments, the mixing chamber 2 comprises one or more second injectors 7 of diluent 8. In the mixing chamber 2, the descending flow 4 comes into contact with the hydrocarbon feedstock 6 atomized using the first injector(s) 5 and optionally with diluent 8, introduced for example by the second injector(s) 7.

[0051] Advantageously, the injection of diluent 8 makes it possible to reduce the partial pressure of the hydrocarbon feedstock and to reduce secondary reactions. Advantageously, the injection of diluent 8 makes it possible to improve the atomization of the hydrocarbon feedstock 6. According to one or more embodiments, the diluent 8 is chosen from the group consisting of water vapor, nitrogen, CO2, light hydrocarbons (e.g. C1-C5 compounds), combustion fumes. According to one or more embodiments, the diluent 8 comprises or consists of water vapor.

[0052] According to one or more embodiments, the pipe 1 is of constant cross-section geometry, such as cylindrical, square, rectangular or hexagonal, or of variable cross-section, such as a truncated pyramid or cone, or a combination of the different geometric shapes. According to one or more embodiments, the pipe 1 is of cylindrical shape and optionally of variable diameter. According to one or more embodiments, the pipe 1 is of at least partially frustoconical shape. According to one or more embodiments, the pipe 1 comprises (in the direction of flow of the solid catalyst): a cylindrical section, for example the diameter of which is chosen to obtain a solid flow of 100 to 800 kg / (m 2 s) and preferably between 300 and 600 kg / (m 2s); a truncated section (called a narrowing section) adjacent to the mixing chamber 2, the diameter of which decreases, for example in order to achieve a solid flow, without taking into account the internals, between 400 and 2000 kg / (m 2 s) and preferably between 700 and 1500 kg / (m 2 s); and optionally a second cylindrical section, for example whose diameter is chosen to obtain a solid flow, without taking into account the internals, between 400 and 2000 kg / (m 2 s) and preferably between 700 and 1500 kg / (m 2 s).

[0053] According to one or more embodiments, the mixing chamber 2 is of constant cross-section geometry, such as cylindrical, square, rectangular or hexagonal, or of variable cross-section, such as a truncated pyramid or cone, or a combination of the different geometric shapes. According to one or more embodiments, the mixing chamber 2 is of cylindrical shape and optionally of variable diameter. According to one or more embodiments, the mixing chamber 2 is of at least partially frustoconical shape. According to one or more embodiments, the mixing chamber 2 comprises an upper limit of cross-section S1 connecting the mixing chamber 2 to the pipe 1 and a lower limit of cross-section S2 connecting the mixing chamber 2 to the downflow reactor 3, the ratio S1 / S2 being less than 0.9 and preferably less than 0.7. According to one or more embodiments, the ratio S1 / S2 is between 0.4 and 0.9, preferably between 0.5 and 0.7.

[0054] According to one or more embodiments, the mixing chamber 2 comprises between 2 and 12 first injectors 5, preferably between 3 and 8 first injectors 5.

[0055] According to one or more embodiments, the mixing chamber 2 comprises between 2 and 12 second injectors 7, preferably between 3 and 8 second injectors 7.

[0056] According to one or more embodiments, the injectors 5 and / or 7 are inclined upwards or downwards or are substantially arranged horizontally.

[0057] According to one or more embodiments, the injectors 5 and / or 7 are inclined upwards, for example with an angle of between 10° and 45° relative to the horizontal.

[0058] With reference to Figure 1, according to one or more embodiments, first injectors 5 and / or second injectors 7 are arranged in one or more horizontal rows, i.e., perpendicular to the central / vertical axis Z of the mixing chamber 2. According to one or more embodiments, second injectors 7 are arranged below (eg a row) first injectors 5. According to one or more embodiments, second injectors 7 are arranged between two rows of first injectors 5.

[0059] According to one or more embodiments, the radial position of the second injectors 7 is in a separation space between the adjacent radial positions of two first injectors 5. According to one or more embodiments, the second injectors 7 are positioned substantially at half the separation angle of two first injectors 5.

[0060] With reference to Figures 2 and 3, according to one or more embodiments, at least one first injector 5 and / or at least one second injector 7 is rotated at an angle a of between 0° and 45°, and preferably of between 10° and 20° relative to the radial direction of the diameter D of the mixing chamber 2, i.e., the projection of the axis of the injectors 7 onto a horizontal plane forms the angle a, with the radial direction of the diameter D of the mixing chamber 2, which is perpendicular to the central / vertical axis Z.

[0061] With reference to Figure 1, the mixing chamber 2 feeds the downflow reactor 3 with a mixture of hydrocarbon feedstock 6, catalyst particles and optionally diluent 8. Advantageously, the hydrocarbon feedstock 6 and the catalyst particles give rise to the cracking reactions which complete each other in the downflow reactor 3 of a length L (along the central / vertical axis Z) to produce a hydrocarbon effluent comprising cracking products, spent catalyst and potentially a portion of the unreacted hydrocarbon feedstock.

[0062] According to one or more embodiments, the downflow reactor 3 is of constant cross-section geometry, such as cylindrical, square, rectangular or hexagonal, preferably cylindrical. According to one or more embodiments, the downflow reactor 3 is of cylindrical shape and optionally of variable diameter. According to one or more embodiments, the diameter of the downflow reactor 3 is defined such that the superficial velocity of the gas passing through it is between 2 m / s and 26 m / s, preferably between 6 m / s and 16 m / s.

[0063] With reference to Figure 4, according to one or more embodiments, the inner wall of the mixing chamber 2 and / or the downflow reactor 3 further comprises a plurality of obstacles 9. Advantageously, the plurality of obstacles 9 is adapted to homogenize the concentration of catalyst particles. Specifically, the obstacles 9 make it possible to redistribute the catalyst particles which can accumulate close to the walls (eg of the mixing chamber 2 and the downflow reactor 3).

[0064] The obstacles 9 may be of various geometric shapes. According to one or more embodiments, the obstacles 9 are in the form of a prism (e.g. prism with a triangular, square, rectangular, hexagonal, circular or elliptical base), or a pyramid (e.g. pyramid with a triangular, square, rectangular, hexagonal, circular or elliptical base), or a truncated cone, the obstacles 9 being positioned discontinuously, for example forming separate elements on the mixing chamber wall 2. With reference to FIG. 4, according to one or more embodiments, the device according to the invention comprises at least one row of obstacles 9, relative to the central / vertical axis Z, arranged at a predetermined height from the internal wall of the mixing chamber 2 and / or the downflow reactor 3. According to one or more embodiments, the obstacles 9 of the row of obstacles 9, thus arranged in a “string”, are positioned substantially equidistant from each other.Advantageously, a row of obstacles 9 comprises (all) the obstacles 9 of a (horizontal) plane perpendicular to the central / vertical axis Z.

[0065] According to one or more embodiments, the obstacles 9 comprise a lower portion (lower end surface) wider than the upper portion (upper end surface).

[0066] According to one or more embodiments, the obstacles 9 are arranged to distribute the catalyst particles towards charge injection zones of the mixing chamber 2, zones more concentrated in hydrocarbons. According to one or more embodiments, the obstacles 9 comprise an upper surface that is oblique and descends laterally, i.e., along the wall of the mixing chamber 2.

[0067] According to one or more embodiments, the obstacles 9 are arranged to distribute the catalyst particles substantially inwards (eg towards the central / vertical axis Z), a zone more concentrated in hydrocarbons. According to one or more embodiments, the obstacles 9 comprise an upper surface that is oblique and descends from the outside towards the inside.

[0068] According to one or more embodiments, obstacles 9 are arranged in the mixing chamber 2 upstream of the at least one first injector 5 of hydrocarbon feedstock 6 and / or of the at least one second injector 7 of diluent 8.

[0069] Advantageously, the obstacles 9 make it possible to direct the catalyst particles towards the injectors and increase the contact, in particular with the hydrocarbon feedstock 6. According to one or more embodiments, the radial position of the obstacles 9 in the mixing chamber 2 is in a separation space between the adjacent radial positions of two (eg first) injectors.

[0070] With reference to Figures 1 to 4, according to the invention, at least a part of the mixing chamber comprises a central space-consuming part 12 (“plug” according to English terminology) arranged substantially along the central / vertical axis Z and defining an annular zone 13 of the mixing chamber 2, through which the catalyst particles pour and / or flow into the mixing chamber 2.

[0071] According to one or more embodiments, the central spacer piece 12 covers the axial position of the first injectors 5. According to one or more embodiments, the central spacer piece 12 covers the axial position of the first injectors 5 and the second injectors 7. Advantageously, the central spacer piece 12 makes it possible to improve the initial contact between the catalyst particles of the descending flow 4 and the hydrocarbon feedstock 6, and to improve the dispersion of the catalyst / feedstock mixture.

[0072] According to one or more embodiments, the central spacer piece 12 is of constant cross-section geometry, such as cylindrical, square, rectangular or hexagonal, or of variable cross-section, such as a truncated pyramid or cone, or a combination of the different geometric shapes. According to one or more embodiments, the central spacer piece 12 has a cylindrical, square, rectangular or hexagonal cross-section, preferably cylindrical, relative to the central / vertical axis Z, and preferably axisymmetric relative to the mixing chamber 2. According to one or more embodiments, the central spacer piece 12 is of circular cylindrical shape. According to one or more embodiments, the central spacer piece 12 is of cylindrical shape and optionally of variable diameter. According to one or more embodiments, the central spacer piece 12 is of at least partially frustoconical shape.According to one or more embodiments, the central spacer 12 comprises a first cylindrical section, a frustoconical section and a second cylindrical section.

[0073] According to one or more embodiments, the central space-saving part 12 is adapted to reduce the passage section of the mixing chamber 2 by 1% to 50% and preferably by 3% to 15% (eg between 6% and 12%), preferably at an axial position covering the axial position of the first injectors 5.

[0074] According to one or more embodiments, the central space-saving part 12 comprises a lower part of section S3 and an upper part 14 of section S4, S3 being greater than S4. According to one or more embodiments, the central space-saving part 12 comprises, from top to bottom, a first cylindrical section, for example section S4, a frustoconical section, for example of section S4 to S3, and a second cylindrical section, for example section S3, S3 being greater than S4.

[0075] According to one or more embodiments, the central spacer 12 extends from the pipe 1 to the mixing chamber 2. Preferably, the central spacer 12 extends from the pipe 1, passes through the mixing chamber 2 and ends in the downflow reactor 3.

[0076] According to one or more embodiments, the part of the central spacer piece 12 which is located in the mixing chamber 2 has a height H1 of between 10% and 100% of the height H2 of the mixing chamber 2. According to one or more embodiments, the lower end 15 of the central spacer piece 12 is below the axial position of the lowest injectors (5, 7) and / or the upper end 16 of the central spacer piece 12 is above the axial position of the highest injectors (5, 7).

[0077] According to one or more embodiments, the lower end 15 of the central space-consuming part 12 is in an axial position arranged below the axial position of the lowest injectors (5, 7), the lower end 15 being able to be extended to the lower end of the mixing chamber 2 or into the downflow reactor 3. According to one or more embodiments, the upper end 16 of the central space-consuming part 12 is in an axial position arranged above the axial position of the highest injectors (5, 7), the upper end 16 being able to be extended to the upper end of the mixing chamber 2 or into the pipe 1.

[0078] The applicant has identified that inefficient penetration of the hydrocarbon feedstock 6 into the downflow 4 of catalyst particles may result in some of the catalyst not mixing with the hydrocarbon feedstock and continuing to flow down the walls of the central bulkhead 12. The flow of solid particles flowing down around the walls of the central bulkhead 12 may result in a significant concentration of solid in the central zone of the downflow reactor 3, which penalizes contact with the hydrocarbon feedstock 6 for the catalytic reaction.

[0079] Advantageously, the applicant has identified that the use of a central bulkhead 12 of specific shape, through the addition of one or more internals 11, makes it possible to redirect the catalyst away from the walls of the central bulkhead 12 and subsequently promotes contact between the two phases.

[0080] With reference to Figures 1 to 4, according to the invention, the at least one internal (11) is arranged on the central space-consuming part (12), and preferably around the central space-consuming part (12), and is arranged at a height (along the central / vertical axis Z) below the at least one first injector (5). Advantageously, the at least one internal 11 is adapted to homogenize the concentration of catalyst particles in the annular zone 13 of the mixing chamber 2. Specifically, the internal(s) 11 make it possible to distribute catalyst particles towards the internal wall of the mixing chamber 2, which can accumulate close to the wall of the central space-consuming part 12. Advantageously, the internals 11 make it possible to distribute the catalyst particles substantially towards the outside (e.g. opposite the central / vertical axis Z), a zone with a higher concentration of hydrocarbons.

[0081] Referring for example to Figure 2, according to one or more embodiments, the internal 11 is annular in shape and is positioned continuously (e.g. in the form of a collar) around the central bulky part 12, i.e., axisymmetrically relative to the central bulky part 12.

[0082] According to one or more embodiments, the continuously positioned internal 11 has a cross-section (in a vertical section along the central / vertical axis Z) in the shape of a triangle, square, rectangle, rhombus, parallelogram, trapezoid, polygon, semicircle, sector, circular segment, elliptical segment, or parabolic segment, among others. According to one or more embodiments, the cross-section of the continuous internal 11 is in the shape of a triangle, for example comprising a substantially horizontal lower side (right triangle), as shown in Figure 4.

[0083] According to one or more embodiments, the internals 11 positioned discontinuously on the central spacer piece are in the shape of a cube, tetrahedron, parallelepiped, prism (e.g. prism with a triangular, square, rectangular, hexagonal, circular or elliptical base), or pyramid (e.g. pyramid with a triangular, square, rectangular, hexagonal, circular or elliptical base), or frustoconical, and, forming separate elements around the central spacer piece 12. According to one or more embodiments, the internals 11 positioned discontinuously on the central spacer piece have a section (according to a vertical section along the central / vertical axis Z) in the shape of a triangle, square, rectangle, rhombus, parallelogram, trapezoid, polygon, semicircle, sector, circular segment, elliptical segment, or parabolic segment, among others.According to one or more embodiments, the section of the discontinuous internals 11 is in the shape of a triangle, comprising for example a substantially horizontal lower side (right triangle).

[0084] With reference to Figure 2, according to one or more embodiments, the continuously positioned internal 11 has a section (according to a horizontal section perpendicular to the central / vertical axis Z) in the form of a ring around the central bulkhead 12.

[0085] Referring for example to Figure 3, according to one or more embodiments, the internals 11 positioned discontinuously have a section (according to a horizontal section perpendicular to the central / vertical axis Z) in the form of a portion of a cylindrical ring (e.g. in the form of a portion of a collar) around the central bulky part 12.

[0086] According to one or more embodiments, the internals 11 are arranged to avoid the accumulation of catalyst particles on the internals 11. According to one or more embodiments, the internals 11 comprise a lower portion (lower end surface) wider than the upper portion (upper end surface). According to one or more embodiments, the internals 11 comprise an upper surface that is oblique and descends laterally (outwards), i.e., along the wall of the central spacer 12. According to one or more embodiments, the upper oblique surface of the internals 11 is straight, convex and / or concave. According to one or more embodiments, the upper oblique surface of the internals 11 forms an angle p of between 10° and 80°, preferably between 30° and 70°, such as substantially 60° relative to the horizontal, as shown in FIG. 4.

[0087] According to one or more embodiments, the at least one internal 11 is arranged on the central space-consuming part 12 downstream of the at least one first injector 5 of hydrocarbon feedstock 6 and optionally of the at least one second injector 7 of diluent 8. Advantageously, the internal(s) 11 make it possible to direct the catalyst particles towards the wall of the mixing chamber 2, under the injectors to increase the contact with the hydrocarbon feedstock 6. According to one or more embodiments, the radial position of the internals 11 on the central space-consuming part 12 is in a separation space between the adjacent radial positions of two (eg first) injectors.

[0088] According to one or more embodiments, the internal(s) 11 are arranged on the central space-consuming part 12 under the first injectors 5 of hydrocarbon charge 6, and optionally the second injectors 7, at an axial distance L (upper end of the internal(s)) from said injectors of between 0*H1 and H1, and preferably between 0.1*1-11 and 0.9*H1.

[0089] According to one or more embodiments, the continuous annular-shaped internals 11 or the rows of discontinuous internals 11 have a height H3 of between 0.02*1-11 and 0.5*1-11, preferably between 0.05*1-11 and 0.3*1-11, very preferably between 0.1*1-11 and 0.2*1-11.

[0090] With reference to Figure 3, according to one or more embodiments, the device according to the invention comprises at least one row of internals 11, relative to the central / vertical axis Z, arranged at a predetermined height on the central space-consuming part 12. According to one or more embodiments, the internals of the row of internals 11, thus arranged in a “string”, are positioned substantially equidistant from each other. Advantageously, a row of internals 11 comprises (all) the internals 11 of a (horizontal) plane perpendicular to the central / vertical axis Z.

[0091] According to one or more embodiments, the perimeter of the internal wall of the central space-consuming part 12, occupied by the row of internals 11, is between 10% and 100% and preferably between 30% and 100%, such as from 60% to 100%.

[0092] According to one or more embodiments, the continuous annular-shaped internal 11 or the row of discontinuous internals 11 is adapted to reduce the passage section of the annular zone 13 by 1% to 50% and preferably by 5% to 35%, such as by 10% to 20%, relative to the passage section of the annular zone 13 without internals 11. According to one or more embodiments, a row of internals 11 comprises at least 1 internal 11, for example between 2 and 16 internals 11, preferably between 3 and 8 internals 11.

[0093] According to one or more embodiments, the central bulk part 12 comprises between 1 and 12 internal 11s of annular shape, such as 1 internal 11 of annular shape.

[0094] According to one or more embodiments, the central space-saving part 12 comprises between 1 and 6 rows of internals 11, such as 2 rows of internals 11 preferably arranged below the (eg first) injectors.

[0095] According to one or more embodiments, the radial position of the internals 11 of a row of internals 11 is in a separation space between the radial position of two adjacent internals 11 of an adjacent row of internals 11, ie, each row of internals 11 has a rotation (along the central / vertical axis Z) relative to an adjacent row of internals 11. According to one or more embodiments, the radial position of the internals 11 of a row of internals 11 has a rotation by an angle between 10° and 35°, preferably between 15° and 30°, relative to the radial position of the internals 11 of an adjacent row of internals 11, and preferably at an angle of 1807N, with N the number of internals in a row of internals 11.According to one or more embodiments, the rows of internals 11 are arranged relative to each other to together cover the entire perimeter of the central space-saving part 12, according to a view along the central / vertical axis Z.

[0096] Referring to Figure 1, according to one or more embodiments, the annular-shaped internals 11 or the rows of discontinuous internals 11 are positioned on axial positions with a distance (the pitch) P from each other of between 0 and 75%, and preferably between 1 and 10%, of the height H2 of the mixing chamber 2. According to one or more embodiments, the distance (the pitch) P separating the axial position of two adjacent internals 11 or the rows of adjacent internals 11 is between 0*H2 and 0.75*H2, preferably between 0.01*H2 and 0.25*H2, very preferably between 0.01*H2 and 0.1*H2.

[0097] The catalyst

[0098] The catalyst is a solid catalyst (e.g. particles of density, size and grain shape chosen for use in a fluidized bed). The densities, sizes and shapes of fluidized bed catalysts are known to those skilled in the art and will not be described further. The catalyst may be any type of catalytic cracking catalyst.

[0099] According to one or more embodiments, the catalyst is an FCC type catalyst, containing for example what is commonly called a matrix made of clay, silica or silica alumina, optionally binder, and / or zeolite, for example from 15% to 70% by weight of zeolite relative to the weight of the catalyst, preferably a Y zeolite and / or a ZSM-5 zeolite. According to one or more embodiments, the catalyst comprises a ZSM-5 zeolite. According to one or more embodiments, the grain density of the catalyst is between 1000 kg / m 3 and 2000 kg / m 3. According to one or more embodiments, the grain density of the catalyst is between 1250 kg / m 3 and 1750 kg / m 3 .

[0100] According to one or more embodiments, the catalyst comprises at least one binder (eg from 30% to 85% by weight) chosen from alumina, silica, silica-alumina, magnesia, titanium oxide, zirconia, clays and boron oxide, alone or as a mixture and preferably from silica, silica-alumina and clays, alone or as a mixture.

[0101] According to one or more embodiments, the catalyst comprises at least one doping element (eg from 0 to 10% by weight) chosen from phosphorus, magnesium, sodium, potassium, calcium, iron, boron, manganese, lanthanum, cerium, titanium, tungsten, molybdenum, copper, zirconium and gallium, alone or as a mixture.

[0102] According to one or more embodiments, the catalyst comprises and / or consists of zeolite, such as ZSM-5, optionally doped.

[0103] The charge

[0104] According to one or more embodiments, the hydrocarbon feedstock 6 is a heavy feedstock, characterized by a boiling onset temperature close to 340°C, often greater than 380°C, such as a heavy cut, for example from a vacuum distillation unit, such as vacuum gas oil / distillate ("vacuum gas oil" or "VGO" according to English terminology) or a vacuum residue, an atmospheric residue, a vacuum gas oil from a conversion unit, such as a coker gas oil ("Heavy Coker Gas Oil" or "HCGO" according to English terminology) or a heavy cut from an ebullated bed or entrained bed hydroconversion unit (such as the H-Oil, LC-Fining, EST, VCC or Uniflex processes), a recycle from a hydrocracking step, alone or in a mixture.

[0105] According to one or more embodiments, the hydrocarbon feedstock 6 is a light feedstock, characterized by a lower boiling point of 450°C, often lower than 400°C, such as a gasoline cut or a diesel cut, for example from an atmospheric distillation unit, or from a conversion unit, such as a gasoline or a diesel from a hydrocracking unit, or a gasoline or a diesel from a coking unit or a gasoline or a diesel from an ebullated bed or entrained bed hydroconversion unit (such as the H-Oil, LC-Fining, EST, VCC or Uniflex processes), or a gasoline or a diesel from an FCC unit, or a recycle from the FCC unit in question, alone or as a mixture. According to one or more embodiments, it is also possible to process a mixture of light and heavy cuts, or even a complete crude.Upon contact with the downflow 4 of hot catalyst particles, the pulverized hydrocarbon feedstock 6 vaporizes and endothermic cracking reactions occur along the downflow reactor 3, thus reducing the temperature and producing: recoverable products (e.g., C1-C4 gas comprising olefins; a gasoline cut comprising aromatics); optionally a light diesel cut (“Light Cycle Oil” or LCO according to English terminology); optionally a heavy diesel cut (“Heavy Cycle Oil” or HCO according to English terminology); optionally an oil in the form of slurry (“slurry” according to English terminology); and optionally a solid residue (coke) adsorbed on the catalyst.

[0106] The method according to the invention

[0107] The process according to the present invention comprises a catalytic cracking step for the production of light olefins (and in particular ethylene and propylene), aromatics (and in particular benzene, toluene and xylenes), and gasoline (and optionally LCO, HCO and slurry), by catalytic cracking of the hydrocarbon feedstock 6 (fed by the first injector 5) by contacting with the descending flow 4 of hot catalyst particles (fed by the line 1), and optionally the diluent 8 (fed by the second injector 7) in the mixing chamber 2 then in the descending flow reactor 3.

[0108] According to one or more embodiments, the downward flow 4 of the catalyst particles in the pipe 1 upstream of the mixing chamber 2 is in a dense fluidized regime and preferably with a mass flow greater than 200 kg / m 2 s, for example to preferably allow a regime with descending bubbles.

[0109] In this application, the term "dense fluidized bed" means a gas-solid fluidized bed operating in a homogeneous regime, in a bubbling regime or in a turbulent regime.

[0110] In the present application, the term "homogeneous fluidized bed" means a gas-solid fluidized bed whose gas velocity is between the minimum fluidization velocity and the minimum bubbling velocity. These velocities depend on the properties of the solid catalyst (density, size, grain shape, etc.). The solid volume fraction is between a value close to 0.45 and the maximum solid volume fraction corresponding to a fixed, non-fluidized bed, generally close to 0.6. In the present application, the term "bubbling fluidized bed" means a gas-solid fluidized bed whose gas velocity is between the minimum bubbling velocity and the transition velocity to the turbulent regime. These velocities depend on the properties of the solid catalyst (density, size, grain shape, etc.). The solid volume fraction is between a value close to 0.35 and a value close to 0.45.

[0111] In this application, the term "turbulent fluidized bed" means a gas-solid fluidized bed whose gas velocity is between the transition velocity to the turbulent regime and the transport velocity. The volume fraction of solid is between a value close to 0.25 and a value close to 0.35.

[0112] In this application, the term "transported fluidized bed" means a gas-solid fluidized bed whose gas velocity is greater than the transport velocity. The solid volume fraction is less than a value close to 0.25. In this application, the term "transport velocity" corresponds to the velocity with which essentially all of the solid is entrained by the gas.

[0113] According to one or more embodiments, the injectors 5 are adapted to atomize the hydrocarbon feedstock 6 (liquid) and penetrate the catalyst flow.

[0114] According to one or more embodiments, the operating conditions of the pipe 1 and / or the downflow reactor 3 are chosen from the following conditions: temperature (at the reactor outlet) between 520°C and 750°C and preferably less than 650°C; absolute total pressure between 0.1 MPa and 0.5 MPa; mass ratio of the catalyst 4 to the hydrocarbon feedstock 6 C / O between 5 (kg / h) / (kg / h) and 35 (kg / h) / (kg / h) and preferably between 15 (kg / h) / (kg / h) and 30 (kg / h) / (kg / h); contact time t c between the hydrocarbon feedstock 6 and the catalyst less than 10 seconds, preferably between 0.5 seconds and 4 seconds; mass flow of catalyst particles between 50 and 850 kg / (m 2 s), preferably between 400 and 750 kg / (m 2 s); and gas surface velocity between 2 m / s and 26 m / s, preferably between 6 m / s and 16 m / s.

[0115] In this description, the contact time tc is defined as the product of the solid volume fraction £ s by bed height H s (eg reactor height L), divided by the superficial gas velocity vsg, this integrated throughout the bed height, as defined below in the mathematical formula Math 1. Math 1

[0116] According to one or more embodiments, a quantity of diluent 8 (e.g. nitrogen and / or water vapor) is added to the feedstock to reduce the partial pressure of hydrocarbons in the feedstock and the diluent is introduced in an amount representing 0% or 0.1% to 40% by weight, preferably 1% to 35% by weight and preferably between 1% and 30% by weight relative to the mass of the hydrocarbon feedstock 6.

[0117] According to one or more embodiments, at the end of the catalytic cracking step in the downflow reactor 3, the gaseous products and the catalyst, and optionally the unconverted vaporized feedstock, are separated in the gas / solid separator (not shown) containing a dense fluidized bed where the cracking reactions can continue.

[0118] According to one or more embodiments, the operating conditions of the separator are chosen from the following conditions: temperature (at the reactor outlet) between 500°C and 750°C, preferably between 550°C and 700°C, even more preferably between 580°C and 685°C; absolute total pressure between 0.1 MPa and 0.5 MPa and preferably between 0.1 MPa and 0.4 MPa and preferably between 0.1 MPa and 0.3 MPa; mass ratio of the catalyst to the feed (unconverted vaporized feed and gaseous products) C / O between 5 (kg / h) / (kg / h) and 40 (kg / h) / (kg / h); contact time tc between the feedstock and the catalyst of between 500 milliseconds (ms) and 10 seconds; and partial pressure of the hydrocarbons of the feedstock (PPHfeedstock) of between 0.01 MPa and 0.3 MPa, preferably between 0.02 MPa and 0.2 MPa and more preferably between 0.05 MPa and 0.15 MPa.

[0119] According to one or more embodiments, at the outlet of the separator the coked catalyst is sent to an optional stripper (not shown) to strip the hydrocarbons remaining adsorbed on the surface of the catalyst using a second diluent.

[0120] According to one or more embodiments, the operating conditions of the stripper are chosen from the following conditions: residence time of the catalyst in the stripper: between 10 seconds and 180 seconds, preferably between 30 seconds and 120 seconds; superficial gas velocity between the minimum fluidization velocity and the transition velocity to the turbulent regime, for example between 0.01 m / s and 0.5 m / s, preferably between 0.15 m / s and 0.4 m / s; solid flux between 25 kg / m 2 s and 200 kg / m 2 s, preferably between 50 kg / m 2 s and 150 kg / m 2 s and preferably between 50 kg / m 2 s and 100 kg / m 2s; temperature between 500°C and 750°C, preferably between 550°C and 650°C; absolute total pressure between 0.1 MPa and 0.5 MPa and preferably between 0.1 MPa and 0.4 MPa and preferably between 0.1 MPa and 0.3 MPa; solid volume fraction between 0.25 and 0.6, preferably between 0.4 and 0.6.

[0121] According to one or more embodiments, at the outlet of the separator or stripper, the coked solid is transported into a regenerator (not shown) in which an air supply burns the coke from the catalyst to produce a hot regenerated catalyst and combustion gases, the hot regenerated catalyst being able to supply the downflow 4 with hot catalyst particles.

[0122] According to one or more embodiments, the operating conditions of the regenerator are chosen from the following conditions: superficial gas velocity between 0.1 m / s and 2 m / s, preferably 0.2 m / s and 1.5 m / s; catalyst residence time between 30 seconds and 20 minutes, preferably between 1 minute and 10 minutes. temperature between 500°C and 840°C, preferably between 650°C and 750°C.

[0123] Examples

[0124] With reference to Figure 5, the flows in a device according to the invention A and a reference device B operating under the reaction-free conditions were compared in order to study the hydrodynamics.

[0125] The device according to the invention A and the reference device B comprise: a pipe 1, composed of a cylindrical section, a narrowing cone and a cylindrical section; a truncated mixing chamber 2 (S3 / S4 being less than 1) comprising a bulky part 12 defining an annular zone 13; a cylindrical downflow reactor 3 having a length of 4.07 m and an internal diameter of 0.42 m, and comprising two rows of 8 obstacles in the form of triangular prisms; four first injectors 5 of hydrocarbon feedstock 6 positioned in counter-current to the downward flow 3 of catalyst particles with an angle of 30° upwards relative to the horizontal, the projection of the first injectors 5 on a horizontal plane being perpendicular to the tangent of the mixing chamber 2; four second injectors 7 of diluent 8 (water vapor) positioned in counter-current to the downward flow 3 of catalyst particles with an angle of 30° upwards relative to the horizontal, the projection of the second injectors 7 on a horizontal plane forming an angle of 45° with the tangent of the mixing chamber 2, the first injectors 5 and second injectors 7 being positioned alternately (on a horizontal plane).

[0126] The device according to the invention has an internal annular-shaped part 11 positioned continuously (e.g. in the form of a triangular-section collar with a horizontal base) around the central bulky part 12.

[0127] The reference device B does not have any internal positioned on the space-consuming part 12.

[0128] The configurations of the device according to the invention A and of the reference device B were simulated in CFD with the Barracuda© tool under the following operating conditions: the catalyst flow of 729 kg / m 2 s; the catalyst has a diameter dso of 73 pm and a grain density of 1418 kg / m 3(ie, group A of the Geldart classification); the air flow rate of 1.85 kg / s has a ratio between the first injectors 5 and the second injectors 7 of 70 / 30; the first injectors 5 are positioned 0.3 m above the upper end of the downflow reactor 3; the rotation angle between the first injectors 5 and the second injectors 7 is 45°; the gas velocity at the outlet of the injectors is 90 m / s for the first injectors 5 and 76 m / s for the second injectors 7; the flow is in ambient conditions without reaction; a spacer 12 is positioned in the center of the mixing chamber 2.

[0129] Figure 5 shows the Mass Fraction of Particles, denoted FMP, for the two configurations A and B of the device according to the invention A and of the reference device B, respectively. Advantageously, the radial distribution of the solid throughout the downflow reactor 3 is always more homogeneous for the device according to the invention A compared to the reference device B. In addition, it is worth noting a significant concentration of the solid in the central zone of the downflow reactor 3, and a low concentration of the solid along the wall of the downflow reactor 3, for the reference device B compared to the device according to the invention A.

Claims

Claims 1. Device for catalytic cracking in a fluidized bed with descending gas-solid co-current comprising, from top to bottom: - a pipe (1) adapted to transport a downward flow (4) of catalyst particles; - a mixing chamber (2) connected to the pipe (1) and adapted to be supplied by the pipe (1) with a downward flow (4), the mixing chamber (2) comprising an internal wall, at least one first injector (5) of hydrocarbon feedstock (6) and a central space-saving part (12) defining an annular zone (13) through which the catalyst particles pass through the mixing chamber (2); and - a descending gas-solid co-current fluidized bed reactor (3) connected to the mixing chamber (2) and adapted to be supplied by the mixing chamber (2) with a mixture comprising catalyst particles and hydrocarbon feedstock (6), device in which the mixing chamber (2) comprises at least one internal (11) on and preferably around the central space-consuming part (12) and arranged under the at least one first injector (5) and being adapted to distribute the mixture towards the wall of the mixing chamber (2).

2. Device according to claim 1, in which the at least one internal (11) is adapted to reduce the passage section of the annular zone (13) by 1% to 35%.

3. Device according to claim 1 or claim 2, wherein the at least one internal (11) is adapted to prevent the accumulation of catalyst particles on said internal (11).

4. Device according to any one of the preceding claims, in which the at least one internal (11) comprises an upper surface oblique and descending towards the outside.

5. Device according to claim 4, wherein the oblique upper surface of the at least one internal (11) is straight, convex and / or concave.

6. Device according to claim 4 or claim 5, in which the oblique upper surface of the at least one internal (11) forms an angle p of between 10° and 80°, relative to the horizontal.

7. Device according to any one of the preceding claims, in which the at least one internal (11) is arranged on the central spacer part (12) at an axial distance (L) of the first injectors (5) of hydrocarbon feedstock (6) between 0*H3 and 1*H3, H3 being the height of the at least one internal (11). Device according to any one of the preceding claims, in which the at least one internal (11) is a plurality of internals (11) positioned discontinuously on the central spacer piece (12). Device according to claim 8, in which the internals (11) are in the shape of a prism, cylinder, pyramid, cone, and / or truncated cone. Device according to claim 8 or claim 9, comprising at least one row of internals (11) arranged at a predetermined height on the central spacer piece (12). Device according to claim 10, in which the perimeter of the central spacer piece wall (12) occupied by the row of internals (11) is between 10% and 100%.A device according to claim 10 or claim 11, wherein the row of internals (11) comprises between 1 and 16 internals (11). A device according to any one of claims 1 to 7, wherein the at least one internal (11) is annular in shape, and is positioned continuously on and around the central bulkhead (12). A device according to claim 13, comprising between 1 and 6 rows of internals (11) and / or between 1 and 12 annular ins (11) arranged at a predetermined height on the central bulkhead (12). A method for descending gas-solid co-current fluidized bed catalytic cracking comprising the following steps:. - transporting a downward flow (4) of catalyst particles in a pipe (1); - supplying a mixing chamber (2) via the pipe (1) with the downward flow (4), the mixing chamber (2) comprising an internal wall, at least one first injector (5) of hydrocarbon feedstock (6) and a central space-saving part (12) defining an annular zone (13) through which the catalyst particles pass through the mixing chamber (2); - feeding a descending gas-solid co-current fluidized bed reactor (3) via the mixing chamber (2) with a mixture comprising catalyst particles and hydrocarbon feedstock (6); and - at least partially cracking the hydrocarbon feedstock (6) in the presence of the catalyst particles in the descending gas-solid co-current fluidized bed reactor (3), to produce an effluent (10) comprising at least partially coked catalyst and gaseous cracking products; - wherein the mixing chamber comprises at least one internal (11) arranged under the at least one first injector (5) and being adapted to distribute the mixture towards the mixing chamber wall (2).

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