FR3140777A1 - Mixing chamber for fluidized bed reactor with downward gas-solid co-current. - Google Patents

Abstract

Device and method for downward gas-solid co-flow fluidized bed catalytic cracking comprising/using: a conduit (1) adapted to convey a downward flow (4) of catalyst particles; a mixing chamber (2) connected to and supplied by the conduit with catalyst particles and comprising an internal wall, at least one first injector (5) of hydrocarbon feed (6) and a central bulk part (12) defining a annular zone (13) through which the catalyst particles pass through the mixing chamber; and a downward gas-solid co-current fluidized bed reactor (3) supplied by the mixing chamber with a mixture comprising catalyst particles and hydrocarbon feed, in which the central bulk part comprises at least one internal (11) arranged under the at least one first injector and being adapted to distribute the mixture towards the wall of the mixing chamber. Figure 1 to be published

Description

Mixing chamber for fluidized bed reactor with downward gas-solid co-current.

The invention relates to the field of refining and petrochemicals and to processes and units for the chemical transformation of petroleum products, in particular hydrocarbon cuts, by Fluidized Bed Catalytic Cracking (“Fluid Catalytic Cracking” or FCC according to Anglo-Saxon terminology) 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.

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

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 gas oil. These compounds are also obtained by fluidized bed catalytic cracking (FCC) of hydrocarbons, such as a Vacuum Distillate (DSV, or “vacuum gas oil” or VGO according to Anglo-Saxon terminology) and/or a residue ( under vacuum or atmospheric) distillation of hydrocarbons and/or naphtha, gas oils, complete crudes.

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

The disadvantages associated with a conventional fluidized bed FCC reactor with ascending gas-solid co-current (“riser” according to Anglo-Saxon terminology) such as back-mixing (“back-mixing” according to Anglo-Saxon terminology) and the accumulation of catalyst in the vicinity of the wall with the consequence of overcracking of the hydrocarbons and the excessive formation of coke, hydrogen, methane and ethane do not make it possible to promote the production of olefins under high severity conditions.

To overcome these drawbacks, the HS-FCC process uses a downflow reactor, where the catalyst and feedstock are set in motion under gravity with a flow that approaches that of a piston-type flow. The downward gas-solid flow in a reactor avoids back-mixing 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 secondary reactions which are responsible for the consumption of such intermediates.

In contrast, downward gas-solid flow presents several major technological challenges, of which a significant challenge corresponds to the flow in the mixing chamber. Indeed, the initial mixture between catalyst and feed conditions the vaporization of the 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 around 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 approximates a perfectly stirred zone.

Patent FR 2 753 453 B1 describes a downward flow cracking reactor comprising a contact zone between the hydrocarbons and the catalyst, and consisting of: a mixing chamber of maximum section S2, placed in communication with means supply of regenerated catalyst through an upper orifice defining a catalyst passage section S1; and a reaction zone of maximum section S4, placed in communication with the mixing chamber by an intermediate orifice of section S3, reactor in which the ratios S2/S1 and S2/S3 are between 1.5 and 8. The patent FR 2 753 453 B1 also describes a bulk part arranged at the lower end of the catalyst conduit supplying the mixing chamber, the bulk part defining an upper annular orifice of the mixing chamber.

Patent application US 2022/0016589 A1 describes a downflow reactor whose feed zone comprises an elongated bulk part on which helical blades are positioned.

Patents US 10,889,768 B2 and US 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) units. -FCC).

In the context previously described, a first object of the present invention is to overcome the problems of the prior art and to provide a device for catalytic cracking in a fluidized bed with a descending gas-solid co-current 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 improved catalyst dispersion between the central zone and the annular zone (i.e., in the proximity of the wall) of the descending gas-solid co-current reactor.

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

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

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

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

According to one or more embodiments, the at least one internal is adapted comprises an upper surface oblique and descending towards the outside.

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

According to one or more embodiments, the oblique upper surface of the at least one internal forms an angle β of between 10° and 80°, relative to the horizontal.

According to one or more embodiments, the at least one internal is arranged on the central bulk part at an axial distance from the first hydrocarbon feed injectors of between 0*H3 and 1*H3, H3 being the height of the at least one intern.

According to one or more embodiments, the at least one internal is a plurality of internals positioned discontinuously on the central bulk part.

According to one or more embodiments, the internals are in the shape of a prism, cylinder, pyramid, cone, and/or truncated cone.

According to one or more embodiments, the device comprises at least one row of internals arranged at a predetermined height on the central bulk part.

According to one or more embodiments, the perimeter of the central bulk room wall occupied by the row of internals is between 10% and 100%.

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

According to one or more embodiments, the at least one internal is of annular shape, and is positioned continuously on and around the central bulky part.

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 bulk part.

According to a second aspect, the aforementioned objects, as well as other advantages, are obtained by a process for catalytic cracking in a fluidized bed with a descending gas-solid co-current comprising the following steps:
- transport a downward flow of catalyst particles in a pipe;
- supply a mixing chamber by the pipe with the descending flow, the mixing chamber comprising an internal wall, at least a first hydrocarbon feed injector and a central bulk part defining an annular zone through which the catalyst particles pass through the mixing chamber;
- supply a fluidized bed reactor with a gas-solid co-current descending through the mixing chamber with a mixture comprising catalyst particles and hydrocarbon feed; And
- at least partially crack the hydrocarbon feed in the presence of the catalyst particles in the fluidized bed reactor with descending gas-solid co-current, to produce an effluent comprising at least partially coked catalyst and gaseous cracking products,
in which the mixing chamber comprises at least one internal disposed under the at least one first injector and being adapted to distribute the mixture towards the mixing chamber wall.

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

There represents an FCC device according to one or more embodiments of the present invention comprising a central bulky part provided with internals for homogenizing the catalyst flow.

There shows a top view of an FCC device according to one or more embodiments of the present invention comprising a mixing chamber in the shape of a truncated cone provided with an internal arranged continuously around the central bulk piece.

There shows a top view of an FCC device according to one or more embodiments of the present invention comprising a mixing chamber in the shape of a truncated cone provided with internals arranged discontinuously around the central bulk piece.

There shows a 3D view of an FCC device according to one or more embodiments of the present invention comprising an internal disposed continuously around the central bulk piece and a plurality of obstacles on the wall of the mixing chamber .

There shows sectional views of the mass fraction of the catalyst in an FCC device according to the invention A as shown in the , and in a reference FCC device B.

Detailed description of the invention

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

In this description, the term “comprising” is synonymous with (means the same as) “comprising”, “include” and “contain”, and is inclusive or open and does not exclude other elements not recited. It is understood that the term “understand” includes the exclusive and closed term “consist”. Furthermore, in the present description, the terms "essentially" or "substantially" or "approximately" correspond to an approximation of ± 10%, preferably ± 5%, most preferably ± 1%.

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

An FCC unit generally treats a heavy cut from the vacuum distillation unit such as a vacuum gas oil or a vacuum residue, or even an atmospheric residue, alone or in a mixture. An FCC unit can also process lighter cuts such as a gasoline cut or a diesel cut, alone or in a mixture. It is also possible to process a mixture of light and heavy cuts, or even a complete rough. In order to increase the yields of propylene and ethylene using high severity reaction conditions (high temperature, very short contact times, high C/O ratios between the catalyst flow rate C and the feed flow rate O), the devices and catalytic cracking processes generally use a fluidized bed reactor with descending gas-solid co-current ("downer" or "down flow reactor" according to Anglo-Saxon terminology), hereinafter called downflow reactor.

However, sometimes downward gas-solid flow presents several technological challenges, including achieving homogeneous flow and mixing in the steady flow section of the descending reactor.

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

The device according to the invention

In reference to the , the device for catalytic cracking in a fluidized bed with a descending gas-solid co-current comprising, from top to bottom:
- a pipe 1 (substantially vertical);
- a mixing chamber 2; And
- a downward flow reactor 3 (substantially vertical).

Line 1 is suitable for supplying mixing chamber 2 with solid catalyst (particles). Line 1 mainly transports solids, as well as a fluidization gas entrained by the descending solid. Pipe 1 presents a flow like a supply column (“standpipe” according to Anglo-Saxon terminology) well known to those skilled in the art.

The mixing chamber 2 is connected to the pipe 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 feed and optionally a thinner.

The downflow reactor 3 is connected to the mixing chamber 2 and is adapted to at least partially crack the hydrocarbon feed 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 charge.

Specifically, with reference to the , the pipe 1 supplies the mixing chamber 2 with a descending flow 4 of (hot) catalyst particles, the mixing chamber 2 comprising a several first injectors 5 of hydrocarbon feed 6. According to one or more embodiments, the or the first injectors 5 are adapted to inject diluent (eg water vapor) with the load. 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 feed 6 atomized using the or first injectors 5 and optionally with diluent 8, introduced for example by the second injector(s) 7.

Advantageously, the injection of diluent 8 makes it possible to reduce the partial pressure of the hydrocarbon feed 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 , CO ₂ , light hydrocarbons (eg C1-C5 compounds), combustion fumes. According to one or more embodiments, the diluent 8 comprises or consists of water vapor.

According to one or more embodiments, the pipe 1 has a constant section geometry, such as cylindrical, square, rectangular or hexagonal, or a variable section, such as a truncated pyramid or cone, or a combination of different geometric shapes. According to one or more embodiments, the pipe 1 is cylindrical in shape and optionally of variable diameter. According to one or more embodiments, the pipe 1 is at least partially frustoconical in shape. According to one or more embodiments, the pipe 1 comprises (in the direction of the flow of the solid catalyst): a cylindrical section, for example whose diameter is chosen to obtain a solid flow of 100 to 800 kg/(m ² s) and preferably between 300 to 600 kg/(m ² s); a frustoconical 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).

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

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.

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.

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

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.

In reference to the , according to one or more embodiments, first injectors 5 and/or second injectors 7 are arranged in one or more horizontal rows, ie, perpendicular to the central/vertical axis Z of the mixing chamber 2. According to one or more several embodiments, second injectors 7 are arranged below (eg a row) of first injectors 5. According to one or more embodiments, second injectors 7 are arranged between two rows of first injectors 5.

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 half of the separation angle of the first two injectors 5.

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 α between 0° and 45°, and preferably between 10° and 20° with respect to the radial direction of the diameter D of the mixing chamber 2, i.e., the projection of the axis of the injectors 7 on a horizontal plane forms the angle α, with the radial direction of the diameter D of the mixing chamber 2, which is perpendicular to the central/vertical axis Z.

In reference to the , the mixing chamber 2 feeds the downflow reactor 3 with a mixture of hydrocarbon feed 6, catalyst particles and optionally diluent 8. Advantageously, the hydrocarbon feed 6 and the catalyst particles give rise to the cracking reactions which occur complete 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 part of the unreacted hydrocarbon feedstock .

According to one or more embodiments, the downward flow reactor 3 has a constant section geometry, such as cylindrical, square, rectangular or hexagonal, preferably cylindrical. According to one or more embodiments, the downward flow reactor 3 is cylindrical in shape and optionally of variable diameter. According to one or more embodiments, the diameter of the downward flow reactor 3 is defined such that the superficial speed of the gas passing through it is between 2 m/s and 26 m/s, preferably between 6 m/s and 16 m/s. s.

In reference to the , according to one or more embodiments, the internal wall of the mixing chamber 2 and/or of the downward flow reactor 3 further comprises a plurality of obstacles 9. Advantageously, the plurality of obstacles 9 is adapted to homogenize the concentration into catalyst particles. Specifically, the obstacles 9 make it possible to redistribute the catalyst particles which can accumulate near the walls (eg the mixing chamber 2 and the downflow reactor 3).

The obstacles 9 can be of varied geometric shapes. According to one or more embodiments, the obstacles 9 are in the shape 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 base, circular or elliptical), or frustoconical, the obstacles 9 being positioned discontinuously, for example forming separate elements on the wall of the mixing chamber 2.

In reference to the , 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 of the internal wall of the mixing chamber 2 and/or the downward flow 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.

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

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 oblique and descending laterally, i.e., along the wall of the mixing chamber 2.

According to one or more embodiments, the obstacles 9 are arranged to distribute the catalyst particles substantially inwards (e.g. towards the central/vertical axis Z), an area more concentrated in hydrocarbons. According to one or more embodiments, the obstacles 9 comprise an upper surface which is oblique and descends from the outside towards the inside.

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 the at least one second injector 7 of diluent 8.

Advantageously, the obstacles 9 make it possible to direct the catalyst particles towards the injectors and increase the contact, in particular with the hydrocarbon feed 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 (e.g. first) injectors.

With reference to Figures 1 to 4, according to the invention, at least part of the mixing chamber comprises a central bulky part 12 ("plug" according to Anglo-Saxon terminology) arranged substantially along the central axis /vertical 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.

According to one or more embodiments, the central bulk part 12 covers the axial position of the first injectors 5. According to one or more embodiments, the central bulk part 12 covers the axial position of the first injectors 5 and the second injectors 7. Advantageously, the central bulk part 12 makes it possible to improve the initial contact between the catalyst particles of the descending flow 4 and the hydrocarbon feed 6, and to improve the dispersion of the catalyst/charge mixture.

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

According to one or more embodiments, the central bulk part 12 is adapted to reduce the passage section of the mixing chamber 2 from 1% to 50% and preferably from 3% to 15% (e.g. between 6% and 12%), preferably in an axial position covering the axial position of the first injectors 5.

According to one or more embodiments, the central bulk 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 bulk part 12 comprises, from top to bottom, a first cylindrical section, for example section S4, a frustoconical section, for example section S4 to S3, and a second cylindrical section, for example section S3, S3 being greater than S4.

According to one or more embodiments, the central bulk part 12 extends from the pipe 1 to the mixing chamber 2. Preferably, the central bulk part 12 extends from the pipe 1, crossing the mixing chamber mixture 2 and ends in the downflow reactor 3.

According to one or more embodiments, the part of the central bulky part 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 one or more embodiments, the lower end 15 of the central bulk part 12 is below the axial position of the lowest injectors (5, 7) and/or the upper end 16 of the part central size 12 is above the axial position of the highest injectors (5, 7).

According to one or more embodiments, the lower end 15 of the central bulk 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 in the downward flow reactor 3. According to one or more embodiments, the upper end 16 of the central bulk part 12 is in an axial position arranged in 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 in line 1.

The applicant has identified that inefficient penetration of the hydrocarbon filler 6 into the descending flow 4 of catalyst particles can result in a portion of the catalyst which does not mix with the hydrocarbon filler and continues to descend all along the walls of the catalyst. the central bulk part 12. The flow of solid particles descending around the walls of the central bulk part 12 can result in a significant concentration of solid in the central zone of the downward flow reactor 3, which penalizes contact with the hydrocarbon feedstock 6 for the catalytic reaction.

Advantageously, the applicant has identified that the use of a central bulky part 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 bulky part. central 12 and subsequently promotes contact between the two phases.

With reference to Figures 1 to 4, according to the invention, the at least one internal (11) is arranged on the central bulk part (12), and preferably around the central bulk 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 towards the internal wall of the mixing chamber. 2 catalyst particles which can accumulate close to the wall of the central bulky part 12. Advantageously, the internals 11 make it possible to distribute the catalyst particles substantially outwards (e.g. opposite the axis central/vertical Z), zone more concentrated in hydrocarbons.

With reference for example to the , according to one or more embodiments, the internal 11 is of annular shape and is positioned continuously (eg in the form of a collar) around the central bulky part 12, ie, axisymmetrically relative to the part central space requirement 12.

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

According to one or more embodiments, the internals 11 positioned discontinuously on the central bulk part are in the shape of a cube, tetrahedron, parallelepiped, prism (e.g. prism with triangular, square, rectangular, hexagonal, circular base or elliptical), or pyramid (e.g. pyramid with a triangular, square, rectangular, hexagonal, circular or elliptical base), or frustoconical, and, by forming separate elements around the central bulk piece 12. According to one or more modes embodiment, the internals 11 positioned discontinuously on the central bulk piece have a section (according to a vertical section along the central/vertical axis Z) in the shape of a triangle, square, rectangle, diamond, 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).

In reference to the , according to one or more embodiments, the continuously positioned internal 11 has a section (in a horizontal section perpendicular to the central/vertical axis Z) in the form of a ring around the central bulky part 12.

With reference for example to the , according to one or more embodiments, the internals 11 positioned discontinuously have a section (in a horizontal section perpendicular to the central/vertical axis Z) in the shape of a cylindrical ring portion (eg in the shape of a collar portion ) around the central bulky part 12.

According to one or more embodiments, the internal(s) 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 part (lower end surface ) wider than the top (upper end surface). According to one or more embodiments, the internal(s) 11 comprise an upper surface oblique and descending laterally (towards the outside), ie, along the wall of the central bulky part 12. According to one or more modes of embodiment, the oblique upper surface of the internal(s) 11 is straight, convex and/or concave. According to one or more embodiments, the oblique upper surface of the internal(s) 11 forms an angle β of between 10° and 80°, preferably of between 30° and 70°, such as substantially 60° relative to the horizontal, such as as shown on the .

According to one or more embodiments, the at least one internal 11 is arranged on the central bulk part 12 downstream of the at least one first injector 5 of hydrocarbon feed 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 contact with the hydrocarbon feedstock 6. According to one or more embodiments, the radial position of the internals 11 on the central bulk part 12 is in a separation space between the adjacent radial positions of two (e.g. first) injectors.

According to one or more embodiments, the internal(s) 11 are arranged on the central bulk part 12 under the first injectors 5 of hydrocarbon feed 6, and optionally second injectors 7, at an axial distance L (high end of the or internal) of said injectors between 0*H1 and H1, and preferably between 0.1*H1 and 0.9*H1.

According to one or more embodiments, the continuous internals 11 of annular shape or the rows of discontinuous internals 11 have a height H3 of between 0.02*H1 and 0.5*H1, preferably between 0.05*H1 and 0 ,3*H1, most preferably between 0.1*H1 and 0.2*H1.

In reference to the , 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 bulk piece 12. According to one or more embodiments, the internals of the row of internals 11, thus arranged in a “rosary”, 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.

According to one or more embodiments, the perimeter of the internal wall of the central bulk 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%.

According to one or more embodiments, the continuous internal 11 of annular shape or the row of discontinuous internal 11 is adapted to reduce the passage section of the annular zone 13 from 1% to 50% and preferably from 5% to 35%, such as from 10% to 20%, relative to the passage section of the annular zone 13 devoid of internal 11.

According to one or more embodiments, a row of internals 11 comprises at least 1 internal 11, for example between 2 and 16 internal 11, preferably between 3 and 8 internal 11.

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

According to one or more embodiments, the central bulk part 12 comprises between 1 and 6 rows of internals 11, such as 2 rows of internals 11 preferably arranged below the (e.g. first) injectors.

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, i.e., each row of internals 11 presents 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 presents a rotation of 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 180°/N, 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 in relation to each other to together cover the entire perimeter of the central bulky part 12, in a view along the central/vertical axis Z.

In reference to the , according to one or more embodiments, the internals 11 of annular shape or the rows of discontinuous internals 11 are positioned in 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, most preferably between 0.01*H2 and 0.1*H2.

The catalyst

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 the catalysts for fluidized beds are known to those skilled in the art, and will not be described further. The catalyst may be any type of catalytic cracking catalyst.

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 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 .

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

According to one or more embodiments, the catalyst comprises at least one doping element (e.g. 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 in mixture.

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

Load

According to one or more embodiments, the hydrocarbon feedstock 6 is a heavy feedstock, characterized by a starting boiling 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 Anglo-Saxon terminology) or a vacuum residue, an atmospheric residue, a vacuum gas oil from a conversion unit, such as a coking gas oil (“Heavy Coker Gas Oil” or “HCGO” according to Anglo-Saxon terminology) or a heavy cut from a hydroconversion unit in a bubbling bed or entrained bed ( such as the H-Oil, LC-Fining, EST, VCC or Uniflex processes), a recycle of a hydrocracking step, alone or in a mixture.

According to one or more embodiments, the hydrocarbon feedstock 6 is a light feedstock, characterized by an end-of-boiling temperature lower than 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 gas oil from a hydrocracking unit, or a gasoline or a gas oil from a coking unit or a gasoline or diesel from a bubbling bed or entrained bed hydroconversion unit (such as the H-Oil, LC-Fining, EST, VCC or Uniflex processes), or gasoline or diesel from a FCC, or a recycle of the FCC unit in question, alone or in mixture. According to one or more embodiments, it is also possible to process a mixture of light and heavy cuts, or even a complete stock.

On contact with the descending flow 4 of hot catalyst particles, the pulverized hydrocarbon feed 6 vaporizes and endothermic cracking reactions occur along the descending flow reactor 3, thus reducing the temperature and producing:
- recoverable products (eg C1-C4 gas including olefins; a gasoline cut including aromatics);
- optionally a light diesel cut (“Light Cycle Oil” or LCO according to Anglo-Saxon terminology);
- optionally a heavy diesel cut (“Heavy Cycle Oil” or HCO according to Anglo-Saxon terminology);
- optionally an oil in the form of mud (“slurry” according to Anglo-Saxon terminology); And
- optionally a solid residue (coke) adsorbed on the catalyst.

The process according to the invention

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 of LCO, HCO and slurry), by catalytic cracking of the hydrocarbon feed 6 (fed by the first injector 5) by contact with the descending flow 4 of hot catalyst particles (fed by line 1), and optionally the diluent 8 (supplied by the second injector 7) in the mixing chamber 2 then in the downflow reactor 3.

According to one or more embodiments, the downward flow 4 of the catalyst particles in line 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 for example preferably allowing a regime with descending bubbles.

In the present 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.

In the present application, the term “homogeneous fluidized bed” means a gas-solid fluidized bed whose gas speed is between the minimum fluidization speed and the minimum bubbling speed. These speeds depend on the properties of the solid catalyst (density, size, shape of the grains, 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 speed is between the minimum bubbling speed and the transition speed to the turbulent regime. These speeds depend on the properties of the solid catalyst (density, size, shape of the grains, etc.). The volume fraction of solid is between a value close to 0.35 and a value close to 0.45.

In the present application, the term “turbulent fluidized bed” means a gas-solid fluidized bed whose gas speed is between the transition speed to the turbulent regime and the transport speed. The volume fraction of solid is between a value close to 0.25 and a value close to 0.35.

In the present 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 the present application, the term “transport speed” corresponds to the speed with which essentially all the solid is carried by the gas.

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

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 (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 catalyst 4 to 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 feed 6 and the catalyst less than 10 seconds, preferably between 0.5 seconds and 4 seconds;
- mass flow of catalyst particles of between 50 and 850 kg/(m²s), preferably between 400 and 750 kg/(m²s); And
- gas surface speed between 2 m/s and 26 m/s, preferably between 6 m/s and 16 m/s.

In the present description, the contact time t _c is defined as the product of the solid volume fraction ɛ _s by the bed height H _s (eg reactor height L), divided by the superficial gas velocity vsg, this integrates everything along the height of the bed, as defined below in the mathematical formula Math 1.

According to one or more embodiments, a quantity of diluent 8 (e.g. nitrogen and/or water vapor) is added to the charge to reduce the partial pressure of hydrocarbons of the charge and the diluent is introduced at a rate of one quantity 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 filler 6.

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 feed, are separated in the gas/solid separator (not shown) containing a dense fluidized bed where cracking reactions can continue.

According to one or more embodiments, the operating conditions of the separator are chosen from the following conditions:
- temperature (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 t _c between the charge and the catalyst of between 500 milliseconds (ms) and 10 seconds; And
- partial pressure of the hydrocarbons of the charge (PPHcharge) between 0.01 MPa and 0.3 MPa, preferably between 0.02 MPa and 0.2 MPa and preferably between 0.05 MPa and 0.15 MPa.

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 by means of a second diluent.

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 speed between the minimum fluidization speed and the transition speed 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 flow 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 ² s ;
- 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.

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 descending flow 4 with hot catalyst particles.

According to one or more embodiments, the operating conditions of the regenerator are chosen from the following conditions:
- superficial gas speed between 0.1 m/s and 2 m/s, preferably 0.2 m/s and 1.5 m/s;
- residence time of the catalyst 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.

Examples

In reference to the , the flows in a device according to the invention A and a reference device B operating under reaction-free conditions were compared in order to study the hydrodynamics.

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 frustoconical 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 shape of triangular prisms;
- four first injectors 5 of hydrocarbon feed 6 positioned countercurrent to the downward flow 3 of catalyst particles with an angle of 30° upwards relative to horizontal, the projection of the first injectors 5 on a horizontal plane being perpendicular to the tangent of mixing chamber 2;
- four second injectors 7 of diluent 8 (water vapor) positioned countercurrent 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).
The device according to the invention has an internal 11 of annular shape positioned continuously (eg in the form of a flange of triangular section with a horizontal base) around the central bulky part 12.

The reference device B does not have any internals positioned on the bulky part 12.

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/m²s;
- the catalyst has a diameter d ₅₀ of 73 µm 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 to 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 angle of rotation between the first injectors 5 and the second injectors 7 is 45°;
- the gas speed leaving the injectors is 90 m/s for the first injectors 5 and 76 m/s for the second injectors 7;
- the flow is under ambient conditions without reaction;
- a bulky part 12 is positioned in the center of the mixing chamber 2.

There presents 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 downward flow reactor 3 is always more homogeneous for the device according to the invention A compared to the reference device B. In addition, it should be noted a significant concentration of the solid on 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 (15)

Device for catalytic cracking in a fluidized bed with a 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) hydrocarbon feedstock (6) and a central bulk part (12) defining an annular zone (13) through which the catalyst particles pass through the mixing chamber (2); And
- a fluidized bed reactor with descending gas-solid co-current (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 load (6),
device in which the mixing chamber (2) comprises at least one internal (11) on and preferably around the central bulk 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). 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) from 1% to 35%. 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). 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. Device according to claim 4, in which the oblique upper surface of the at least one internal (11) is straight, convex and/or concave. Device according to claim 4 or claim 5, in which the oblique upper surface of the at least one internal (11) forms an angle β of between 10° and 80°, relative to the horizontal. Device according to any one of the preceding claims, in which the at least one internal (11) is arranged on the central bulk part (12) at an axial distance (L) from the first injectors (5) of hydrocarbon charge ( 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 bulk part (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 bulk part (12). Device according to claim 10, in which the perimeter of the central bulk room wall (12) occupied by the row of internals (11) is between 10% and 100%. Device according to claim 10 or claim 11, in which the row of internals (11) comprises between 1 and 16 internals (11). Device according to any one of claims 1 to 7, in which the at least one internal (11) is of annular shape, and is positioned continuously on and around the central bulky part (12). Device according to claim 13, comprising between 1 and 6 rows of internals (11) and/or between 1 and 12 internals (11) of annular shape arranged at a predetermined height on the central bulk piece (12). Process for catalytic cracking in a fluidized bed with descending gas-solid co-current comprising the following steps:
- transport a downward flow (4) of catalyst particles in a pipe (1);
- supply a mixing chamber (2) via pipe (1) with the downward flow (4), the mixing chamber (2) comprising an internal 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 (2);
- supply a fluidized bed reactor with a descending gas-solid co-current (3) through the mixing chamber (2) with a mixture comprising catalyst particles and hydrocarbon feed (6); And
- at least partially crack the hydrocarbon feed (6) in the presence of the catalyst particles in the downward gas-solid co-current fluidized bed reactor (3), to produce an effluent (10) comprising at least partially coked catalyst and gaseous cracked products;
- in which the mixing chamber comprises at least one internal (11) disposed under the at least one first injector (5) and being adapted to distribute the mixture towards the wall of the mixing chamber (2).