EP1242569B1 - Method and device for catalytic cracking comprising in parallel at least an upflow reactor and at least a downflow reactor - Google Patents

Abstract

An apparatus and a process for catalytic cracking of a hydrocarbon feed is described, carried out in at least two reaction zones, one ( 30 ) operating in catalyst riser mode, wherein the feed and catalyst from regeneration zone ( 3 ) are circulated from bottom to top, the first gases produced are separated from the coked catalyst in a first separation zone ( 38 ), the catalyst is stripped ( 40 ), a first cracking and stripping effluent ( 42 ) is recovered and the coked catalyst is recycled ( 45 ) to the regeneration zone. Catalyst ( 12 ) from regeneration zone ( 3 ) and a hydrocarbon feed ( 19 ) are introduced into the upper portion of a dropper reaction zone ( 16 ), the catalyst and feed being circulated from top to bottom, the coked catalyst is separated from the second gases produced in a second separation zone ( 20 ), the second gases ( 24 ) produced are recovered and the coked catalyst is recycled ( 25 ) to the regeneration zone.

Description

The present invention relates to a process and apparatus for catalytic cracking (FCC) entrained bed comprising parallel reactors comprising at least one downflow reactor (dropper) and at least one upflow catalyst reactor (commonly called riser) from at least one regeneration zone.

The evolution of refining is marked more and more by the required flexibility of the units from the point of view of the charges to be treated but also by the versatility of the effluents produced.

Thus the FCC had to evolve to accept increasingly heavy loads (carbon conradson up to 10 and d ₄ ¹⁵ up to 1.0 for example) and that at the same time it was asked d increase its efficiency in petrol cut, but also in propylene, the need of which increased in petrochemicals.

The specific characteristics of catalytic cracking units with dual regeneration with charge injection in the form of fine droplets met the need to work on heavy cuts.

More recently, and in the same direction, has been added to this unit a heat extraction module (heat exchanger catcooler), allowing by its extraction of calories to process loads without high limit of carbon conradson. Still in the same optics of heavy load processing, the concept of downstream reactor with a short residence time (0.1 to 1 second) has been developed and patented, making it possible to reach severe cracking conditions (for example high temperature up to at 650 ° C. and large catalyst circulation - catalyst to filler or C / O ratio of 10 to 20 -) The severe cracking conditions make it possible to maximize the conversion. However, in order to obtain a good selectivity, it becomes essential to control and limit the residence time of the hydrocarbons in the reactor to prevent the thermal degradation reactions from becoming predominant (excessive production of coke, loss of products recoverable by over-coating) . The contacting of the hydrocarbons with the catalyst must be carried out correctly with a time of contact between the catalyst and the limited hydrocarbons. The downstream reactor, combined with a appropriate mixing system as described in the patent PCT / FR97 / 01627 , makes it possible to optimize selectivities in recoverable products (LPG, gasolines) by minimizing non-recoverable products such as coke and dry gases compared to a conventional technology.

To meet the goal of flexibility, the idea then appeared to combine a traditional riser with a dropper short stay. The patent application FT98 / 14319 describes a series of a dropper and a riser in series. It describes in detail the advantages of a second reactor which is operated under conditions very different in temperature and in C / O of the main riser: in particular, this second reactor advantageously represents an additional capacity of treatment of a heavy load in producing a minimal amount of coke compared to a conventional reactor; it also becomes possible to crack some cuts (called recycles) from the main riser undesirable (low recovery or cuts not meeting certain specifications such as sulfur or aromatic content) to maximize the yield of valuable cuts (LPG, gasoline) .

In an example of this patent, the fresh feed is introduced at the bottom of the riser and it is the LCO product of the riser which is introduced as load of the dropper. Such a configuration makes it possible to maximize the gasoline yield by depleting the LCO under relatively severe cracking conditions. But the disadvantage of this system with a dropper and a riser in series is that for a large load capacity dropper, the riser reactor works with a significant amount of partially deactivated catalyst through its passage into the dropper (the deactivation from the coke deposition on the catalyst). This results in decreased efficiency that does not allow to draw the full potential of this association. The other patented configuration by Stone and Webster is to implement two risers in parallel by working from regenerated catalyst in a common regeneration zone. Several types of interconnections of recycles are possible between the two risers, but here are substantially similar cracking conditions (C / O, exit temperature and residence time) that do not allow to treat in one of the risers a truly refractory cut and amenable to cracking under severe conditions (eg HCO).

Thus, according to the patent US 5009769 there is disclosed a unit comprising two upflow catalytic reactors operating in parallel, in which regenerated catalyst flows in a regeneration zone comprising two regenerators. This unit would be suitable for handling a wide variety of feeds but it operates under substantially the same catalyst circulation conditions (C / O = 5 to 10 and residence time 1 to 4 s for the first reactor and C / O = 3 to 12 and residence time 1 to 5 s for the second reactor). Under these conditions, the range of products obtained by each of the two reactors is substantially the same.

The patent US 4116814 also illustrates the case of two upflow reactors connected in parallel to a particle regenerator. US-500976 describes hydrocracking processes in ascending reactors.

The idea presented in this patent is to derive the full potential of paralleling a riser operating under conventional cracking conditions (eg C / O 5 to 7, exit temperature 510). at 530 ° C, residence time 1-2 s) and a dropper operating under severe cracking conditions (eg C / O 10-20, exit temperature 560-620 ° C; stay of 0.2 to 0.5 s). This combination makes it possible to recycle the HCO or LCO produced in the riser, which are refractory charges that are difficult to crack, in order to maximize the production of gasoline. But it also makes it possible to maximize the production of olefins and in particular propylene by recycling the gasoline or just a fraction of the gasoline (heavy or light) produced by the riser.

An object of the invention is to overcome the disadvantages of the prior art. The object of the invention is described in the claims of independent claims 1 and 12. Optional features of the invention are described in the claims of dependent claims 2-11 and 13-16.

Another object is to crack both heavy hydrocarbons and light hydrocarbons under severe reaction conditions, in a reactor adapted to this type of conditions, the dropper or downflow reactor and much less severe in a riser or reactor. upflow so as to promote the formation of very different products meeting the specificities of each type of reactor.

It has been found that, for example, more propylene can be obtained simultaneously by means of a downflow reactor operating in severe catalytic cracking conditions and more gasoline through an upflow reactor operating under less severe cracking conditions, economically, from a cracking unit having at least one catalyst regeneration step and the combination of said reactors operated in parallel on at least one regenerator.

More specifically, the invention relates to a process for catalytic cracking in a fluidized or fluidized bed of at least one hydrocarbon feedstock in at least two reaction zones, at least one having an upward flow, into which the feedstock is introduced and of the catalyst from at least one regeneration zone in the lower part of the upflow reaction zone, the feedstock and the catalyst are circulated from bottom to top in said zone, the first gases produced from the coked catalyst are separated in a the first separation zone, the catalyst is stripped by means of a stripping gas, a first cracking and stripping effluent is recovered and the coked catalyst is recycled to the regeneration zone and regenerated at least partly by means of an oxygen-containing gas, the process being characterized by introducing catalyst from at least one regeneration zone and a hydrocarbon feedstock formed in the upper part of at least one downflow reaction zone, the catalyst and the feed are circulated up and down under suitable conditions, the coked catalyst is separated from the second produced gases in a second separation zone, the second product gases are recovered and the coked catalyst is recycled to the regeneration zone.

According to a characteristic of the process, the temperature of the catalyst at the outlet of the downstream reactor may be greater than that at the outlet of the riser reactor.

According to another advantageous feature, the catalyst from the second separation zone can be stripped by means of a recycle gas which is usually steam and the resulting hydrocarbons are recovered in general with the cracking gases.

It is preferable to regenerate the coked catalyst in two consecutive regeneration zones, each of which has its own combustion gas evacuation resulting from the regeneration of the coke catalyst. The catalyst to be regenerated from the first separation zone is introduced into a first regeneration zone operating at a suitable temperature, the at least partially regenerated catalyst being sent to the second regeneration zone operating at a higher temperature and the catalyst regenerated from the second regeneration zone is introduced into the upflow reaction zone and the downflow reaction zone.

The coke catalyst from the second separation zone may be recycled to the first regeneration zone either by gravity flow, generally in the dense zone, or by flow through a riser comprising fluidizing air as a motor ( lift), usually in the diluted zone of the first regeneration zone.

It may be advantageous to recycle the catalyst from the second separation zone into the second regeneration zone by means of a lift, either in its dense zone or in its diluted zone.

The hydrocarbon feedstock or each of the feeds, if different, can be introduced into the upward reaction zone and the downward reaction zone by co-current injection of the catalyst flow or countercurrent, or countercurrently. current for one and co-current for the other. Nevertheless, a countercurrent injection in the two zones seems preferable for a better vaporization of the introduced droplets.

• Dans la zone réactionnelle ascendante (RA) :
  • température du catalyseur (sortie RA) : 500-550 °C.
  • catalyseur/charge (C/O) : 4-9 et de préférence 5-7.
  • temps de séjour : 0,5-4 s, de préférence 1-2 s
• Dans la zone réactionnelle descendante (RD) :
  • température du catalyseur (sortie RD) = 560-620 °C ;
  • C/O : 8-20, de préférence 10-15 ;
  • temps de séjour ; 0,1-2 s, de préférence 0,2-1 s

The operating conditions for catalytic cracking of the feeds are usually as follows:

• In the upward reaction zone (AR):
  • catalyst temperature (output RA): 500-550 ° C.
  • catalyst / charge (C / O): 4-9 and preferably 5-7.
  • residence time: 0.5-4 s, preferably 1-2 s
• In the downward reaction zone (RD):
  • catalyst temperature (RD output) = 560-620 ° C;
  • C / O: 8-20, preferably 10-15;
  • residence time ; 0.1-2 s, preferably 0.2-1 s

The feedstock supplying each of the reaction zones may be a so-called fresh non-cracked feedstock, a recycle of a part of the products resulting from a fractionation downstream or a mixture of the two.

The charge of one of the reaction zones may be either heavier or lighter than that flowing in the other zone. More particularly, the charge of the upflow reaction zone may be a vacuum distillate or an atmospheric residue or a recycle of a portion of the products from the downward reaction zone and the charge of the downflow zone is a non-feedstock. or a recycle of a portion of the products from the upward reaction zone and preferably a gasoline cut or an LCO cut.

According to a characteristic of the process, the flow of charge and for example recycle (LCO cut, HCO or gasoline) circulating in the downstream reactor may represent less than 50% by weight of the feed rate to be converted in the upward reaction zone.

• La possibilité de traiter par la boucle dropper n'importe quelle charge fraîche ou recyclée dans des conditions de craquage sévères indépendantes des conditions de craquage du riser.
• La simplicité opératoire de la boucle dropper puisqu'elle est indépendante de la boucle riser.
• La simplicité de mise en oeuvre de la boucle dropper puisque celle-ci peut être placée n'importe où autour du régénérateur, à condition de satisfaire le bilan pression. Ceci serait pratiquement impossible à réaliser avec un second riser, parallèle au premier car le bilan pression impose dans ce cas une hauteur minimale, donc un temps de séjour qui ne peut descendre aux valeurs typiques d'un dropper (inférieur à la seconde). En d'autres termes, il est très difficile en pratique de réellement différencier les conditions de craquage de deux risers fonctionnant en parallèle.
• La boucle dropper peut être adaptée à la plupart des unités de craquage existantes, à un ou deux régénérateurs et/ou avec une technologie de séparation, de stripage et de transfert du catalyseur la mieux adaptée aux exigences du client.
• Optimisation des sélectivités en produits valorisables (LPG, essences) grâce à la technologie du réacteur descendant en minimisant les sélectivités en produits non valorisables tels que le coke et les gaz secs par rapport à une technologie conventionnelle tout en maximisant la conversion grâce à l'obtention de conditions de sévérité très importante au dropper.
• Chaque réacteur (dropper, riser) travaille avec du catalyseur fraîchement régénéré.
• Il y a indépendance des conditions opératoires de chaque réacteur, en particulier en terme de C/O, ce qui n'est pas le cas dans la configuration série.
• Il n'y a aucun problème de régulation des conditions de craquage propres à chaque réacteur en terme de température de sortie du réacteur puisqu'il n'y a plus de couplage comme dans la configuration réacteurs en série.
• La production d'un effet de refroidissement du catalyseur due à la boucle dropper. En effet, pour une charge donnée, il existe à partir d'un certain niveau de circulation dans le dropper (C/O) un effet d'extraction de chaleur, c'est-à-dire une diminution des températures au régénérateur, ou au premier ou au second régénérateur s'il s'agit d'une structure à double étage de régénération suivant le régénérateur vers lequel s'effectue le retour du catalyseur coké issu du dropper.

The advantages of the configuration according to the present invention are as follows:

• The ability to process through the dropper loop any fresh or recycled feed under severe cracking conditions independent of the cracking conditions of the riser.
• The operational simplicity of the dropper loop since it is independent of the riser loop.
• The simplicity of implementation of the dropper loop since it can be placed anywhere around the regenerator, provided to satisfy the pressure balance. This would be practically impossible to achieve with a second riser, parallel to the first because the pressure balance imposes in this case a minimum height, so a residence time that can not fall to the typical values of a dropper (less than the second). In other words, it is very difficult in practice to really differentiate the cracking conditions of two risers operating in parallel.
• The dropper loop can be adapted to most existing cracking units, one or two regenerators and / or with a catalyst separation, stripping and transfer technology best suited to customer requirements.
• Optimization of selectivities in recoverable products (LPG, gasolines) thanks to the technology of the downstream reactor by minimizing selectivities in non-recoverable products such as coke and dry gases compared to a conventional technology while maximizing the conversion by obtaining conditions of very severe severity dropper.
• Each reactor (dropper, riser) works with freshly regenerated catalyst.
• There is independence of the operating conditions of each reactor, in particular in terms of C / O, which is not the case in the series configuration.
• There is no problem in regulating the cracking conditions specific to each reactor in terms of outlet temperature of the reactor since there is no longer coupling as in the series reactor configuration.
• The production of a cooling effect of the catalyst due to the dropper loop. Indeed, for a given load, there exists from a certain level of circulation in the dropper (C / O) a heat extraction effect, that is to say a decrease in temperatures to the regenerator, or the first or second regenerator if it is a regeneration double-stage structure following the regenerator to which the return of the coked catalyst from the dropper.

Indeed, the downstream reactor technology makes it possible to minimize the amount of coke formed. This results in a much lower coke content on the catalyst than in an equivalent upflow reactor. Combined with appropriate operating conditions where the circulation of catalyst is higher compared to the same amount of filler (high C / O), the coke content is thus very significantly reduced so that the amount of heat released by the combustion of this additional coke in the regenerator (s) is significantly lower than the amount of heat consumed by the vaporization of the feedstock and the heat of reaction to the dropper reactor. Overall, the regeneration side catalyst is cooled compared to the previous situation comprising only one traditional riser.

This heat extraction effect, which can be obtained equivalently by a heat exchanger on the regeneration side (catcooler) or by the vaporization of an almost chemically inert recycle (MTC) downstream of the charge injection in the direction of the flow of the catalyst in a riser or dropper reactor, allows either to treat loads with higher carbon conradson, or to increase the flow of charge, or to take advantage of the temperature decrease at (x) regenerator (s) ) to increase the circulation of catalyst (C / O) to riser and dropper. Indeed, the heat required for the reaction and the reaction side vaporization is provided by the regenerated catalyst, heated by combustion of the coke regenerator (s). In order to maintain a constant reactor output temperature, the heat extraction effect makes it necessary to increase the circulation of catalyst with a constant charge flow rate and thus to benefit from better catalytic activity (more active sites). It is also possible to treat more refractory charges in the dropper.

For all these reasons, the combination of a riser and a dropper in parallel on a common regeneration device is very interesting, both in renovating existing units (revamping) and building new units.

• Au moins un réacteur ascendant sensiblement vertical ayant une entrée inférieure et une sortie supérieure :
• un premier moyen d'alimentation en catalyseur régénéré connecté à au moins un régénérateur de catalyseur coké et raccordé à ladite entrée inférieure ;
• un premier moyen d'alimentation en la charge disposé au dessus de l'entrée inférieure du réacteur ascendant ;
• une première enceinte de séparation de catalyseur coké et d'une première phase gazeuse raccordée à la sortie supérieure du réacteur ascendant, ladite enceinte de séparation comportant une chambre de stripage du catalyseur et ayant une sortie supérieure d'une phase gazeuse et une sortie inférieure de catalyseur coké et strippé, ladite sortie inférieure étant connectée au régénérateur de catalyseur via des premiers moyens de recyclage du catalyseur;

The invention also relates to a catalytic cracking device in a fluidised or driven bed of a hydrocarbon feedstock comprising:

• At least one substantially vertical riser reactor having a lower inlet and an upper outlet:
• first regenerated catalyst feed means connected to at least one coked catalyst regenerator and connected to said lower inlet;
• first feed means disposed above the bottom inlet of the riser reactor;
• a first coked catalyst separation chamber and a first gaseous phase connected to the upper outlet of the upflow reactor, said separation chamber comprising a catalyst stripping chamber and having an upper gas phase outlet and an outlet lower coked and stripped catalyst, said lower outlet being connected to the catalyst regenerator via first catalyst recycle means;

• un second moyen d'alimentation en catalyseur régénéré connecté au dit régénérateur de catalyseur coké et raccordé à ladite entrée supérieure du réacteur descendant ;
• un second moyen d'alimentation en la charge disposé au-dessous du second moyen d'alimentation ;
• une deuxième enceinte de séparation du catalyseur coké d'une seconde phase gazeuse raccordée à la sortie inférieure du réacteur descendant et ayant une sortie de la seconde phase gazeuse et une sortie de catalyseur coké, et des seconds moyens de recyclage du catalyseur coké raccordés à ladite sortie de catalyseur de la deuxième enceinte de séparation et connectés au régénérateur.

the device being characterized in that it comprises at least one substantially vertical downflow reactor having an upper inlet and a lower outlet;

• second regenerated catalyst supply means connected to said coked catalyst regenerator and connected to said upper inlet of the downstream reactor;
• second feed means disposed below the second feed means;
• a second separation chamber of the coked catalyst of a second gas phase connected to the lower outlet of the downstream reactor and having a second gas phase outlet and a coked catalyst outlet, and second coke catalyst recycling means connected to said catalyst outlet of the second separation chamber and connected to the regenerator.

According to a variant of the device, the second chamber for separating the catalyst from the cracking effluents may not comprise a stripping chamber. In this case, prestriping means for example by steam can be introduced into the separation chamber and the evacuation of the steam can be carried out with the effluents of cracking and prestriping.

According to another variant, the second separation chamber comprises a catalyst stripping chamber with stripping vapor injection, in communication with it, as described for example in the Applicant's patent application. FR 98/09672 . The cracking and stripping effluents are generally discharged by common means.

According to another advantageous feature of the device, it may comprise two superposed regenerators of coked catalyst, the second being located above the first, means of circulation of the catalyst from the first regenerator to the second regenerator. Said first and second catalyst supply means are connected to the second regenerator and the lower outlet of the first separation chamber is connected to the first regenerator via the first recycling means.

The invention will be better understood from the attached figure which illustrates a particularly advantageous embodiment of the device comprising two superimposed coked catalyst regenerators, connected in parallel with two catalytic cracking reactors, one with upward flow (riser) and the other downflow catalyst (dropper).

According to the figure, a regeneration zone (1) of the coked catalyst comprises two superposed regeneration chambers (2) and (3) in which the catalyst is regenerated in a fluidized bed, air being introduced at the base of each enclosure by means not shown in the figure. Each chamber has its own dedusting means (4, 5) (cyclones) and evacuation (9, 10) of the coke combustion effluents. The pressure in each chamber (2) and (3) can be controlled by valves on the lines allowing the evacuation of combustion effluents at least partially dusted. The catalyst is transported between the two chambers by means of an ascending column (6). Air, generally introduced at the base by an injector (7), at a sufficient speed makes it possible to transport the catalyst between the two enclosures. Typically, the proportion of air required for regeneration is 30 to 70% in the lower chamber (2) operating at a lower temperature (670 ° C. for example) and 15 to 40% in the upper chamber (3). ) operating at higher temperature (770 ° C for example), 5 to 20% of air flowing in the lift to transport the catalyst. A valve on a solid (8) valve cap type to control the flow rate between the speakers (2) and (3).

The substantially regenerated catalyst from the second regenerator located above the first (3) is sent from a dense bed (11) into a disengaging well (13) through a conduit (12) inclined at an angle usually between 30 and 70 degrees from the horizontal. In the well (13), the circulation of the catalyst is slowed down to allow any gas bubbles to be evacuated to the second regeneration chamber (3) through a pressure equalizing line (14). The catalyst is then accelerated and descends through a transfer tube (15) to the inlet of a reactor (16) with downward flow (dropper). Throughout its journey from the regeneration chamber, the catalyst is maintained in the fluidized state by adding small amounts of gas throughout the transport. If the catalyst is thus maintained in the fluidized state, this makes it possible to obtain at the inlet of the dropper a pressure greater than that of the fumes coming from the external cyclones (5).

The dropper (16) comprises means for introducing the regenerated catalyst (17), which may be a solid-state valve, an orifice or simply the opening of a conduit, into a contact zone (18) located below the valve (17), where the catalyst encounters against the current for example, the hydrocarbon feed introduced by injectors (19), generally consist of atomizers where the load is finely divided into droplets through the introduction of auxiliary fluids such as water vapor. The means for introducing the catalyst are situated above the means for introducing the charge. Between the contacting zone (18) and the means for separating the hydrocarbons from the catalyst (20), it is possible to have a substantially elongated reaction zone (21), represented vertically in the figure, but this condition is not exclusive. The average residence time of the hydrocarbons in the zones (18) and (21) will for example be less than 650 ms, preferably between 50 and 500 ms. The effluents of the dropper are then separated in the separator (20), for example as described in the application FR98 / 09672 where the residence time must be limited to the maximum. The gaseous effluents (cracked gases) from the separator can then undergo an additional step of dedusting through cyclones, for example external cyclones (22), arranged downstream on a line (23). These gaseous effluents (cracked gases) are evacuated by a line (24). It is also possible to cool the gaseous effluents, in order to limit the thermal degradation of the products, for example by injecting liquid hydrocarbons into the effluent exiting for example cyclones (22) via the line (24) or directly at the outlet of the cracked gas from the separator (20) upstream of said cyclones. The catalyst separated in the separator (20) is then either reinjected directly to the base of a riser (25) through a conduit (26), a valve (27) controls the flow rate in relation to the outlet temperature of the dropper introduced into a fluidized bed (28) of stripping through a conduit or opening (30). The catalyst in the fluidized bed. (28) then undergoes stripping (contact with a light gas such as water vapor, nitrogen, ammonia, hydrogen or even hydrocarbons whose carbon number is less than 3) by means which are well described in the prior art before being transferred to the riser (25) through the conduit (26). The gaseous stripping effluents are generally discharged from the fluidized bed (28) through the same means (23, 22) which allow the evacuation of gaseous effluents from the dropper (16) via the line (24). The coked catalyst is raised by a fluidization gas (29) in the dense fluidized bed of the second regenerator (3).

The riser reaction zone (30) is a substantially elongated tubular zone, many examples of which are described in the prior art. In the example given in the figure, the hydrocarbon charge is introduced by means (31), generally consisting of atomizers where the charge is finely divided into droplets, generally using the introduction of auxiliary fluids such as as water vapor, introduced through the means (31). The means for introducing the catalyst are located below the feed introduction means. The feed introduction is located above the catalyst inlet.

These means for introducing the catalyst into the riser (30) comprise a withdrawal well (32) conforming to that (13) which feeds the dropper, connected to the dense bed of the second catalyst regenerator (3) via a conduit (33) inclined at substantially the same angle as that of the conduit (12). The well (32) is further connected to the diluted fluidized bed by a pressure equalizing line (34). At the base of the well, a line (35) first vertical and then inclined is connected to the lower part of the riser. A control valve (36) disposed on the line (35) regulates the regenerated catalyst flow at the inlet of the riser as a function of the catalyst outlet temperature and the effluents at the top of the riser. Fluidizing gas introduced at the base of the riser by injection means (37) circulate the catalyst cocurrently with the charge in the riser. According to a variant not shown, the load could have been injected against the current flow down the riser. Above the charge injectors, an injection of a light cut of hydrocarbons or a heavier cut (LCO or HCO for example), from downstream distillation of the riser cracking effluents can be carried out in this riser. The cut introduced can represent 10 to 50% by weight of the feed introduced into the riser and can contribute to maximize the production of gasoline.

The cracking reaction is carried out in the riser. The cracking effluents are then separated in a separator (38), for example as described in the application PCT FR 98/01866 . The catalyst resulting from the separation is then introduced into a fluidized bed (39) of a stripping chamber (40) located below the separator, through conduits (41) or openings. The catalyst in the chamber (39, 40) is then subjected to stripping (contact with a light gas such as water vapor, nitrogen, ammonia, hydrogen or even hydrocarbons with a number of carbon atoms of less than 3) by means not shown in the figure.

The stripped catalyst is then transferred to the dense bed of the first regeneration chamber (2) via a conduit (45). The gaseous cracking and stripping effluents separated in the separator (38) are discharged through a conduit (42) to a secondary separator (43) such as a cyclone for example internal to the chamber (39, 40) before be directed to the downstream fractionation section by a conduit (44).

By way of example and to illustrate the invention, the results obtained were compared by an industrial unit equipped with a conventional upstroke reactor treating a heavy load and equipped with a double regeneration system as described in the figure with the results obtained by inserting a downstream reactor in parallel, the new reactor then being fed by two sections, different in each example, produced by the upstream reactor.

The results of this comparison are based on the industrial results obtained with the unit equipped with the upstream reactor and cracked pilot tests of the section under consideration. The new conditions to satisfy the thermal balance of the unit as a whole are recalculated with a process model.

• Densité d¹⁵ : 0,937
• Teneur en soufre : 0,5 %
• Carbone conradson : 5,8 %

The fresh batch (vacuum distillate) has the following characteristics:

• Density d ¹⁵ : 0.937
• Sulfur content: 0.5%
• Carbon conradson: 5.8%

• Granulométrie : 70 micromètres
• Surface BET(m²/g) : 146
• Surface zéolitique Y (m²/g) : 111
• Surface de la matrice (m²/g) : 35

It is injected at the base of a riser which is supplied with catalyst from a dual regeneration device, according to the figure presented in the present invention. This catalyst, based on zeolite Y has the following characteristics:

• Particle size: 70 micrometers
• BET surface area (m ² / g): 146
• Zeolite area Y (m ² / g): 111
• Surface of the matrix (m ² / g): 35

The catalyst comes from the second regenerator.

The cracking effluents are distilled and a portion of the HCO cut obtained as well as all of a heavy gasoline cut (170 ° C-200 ° C) are recycled into the riser. This recycle, consisting of 49.3% HCO and 50.7% heavy gasoline cut, represents 27.1% by weight of the fresh load riser. An additional cut is recycled as a feed into the dropper which is fed, in turn, by catalyst from the second regenerator.

The coked catalyst from the stripper connected to the riser is recycled in the dense phase of the first regenerator while the one from the stripper connected to the dropper is recycled by means of a lift in the dense phase of the second regenerator.

Example 1

In this first example, 23.4% weight of the gasoline cut produced at the riser, ie 10% by weight relative to the fresh load at the riser, is recycled as a load in the dropper.

The conditions are maintained at riser (ROT and recycle) by increasing the C / O of the riser.

• RA = réacteur ascendant (temps de séjour : 1 s)
• RD = réacteur descendant (temps de séjour : 0,4s)
• REG1 = première enceinte de régénération
• REG2 = deuxième enceinte de régénération

RA seul RA + RD Charge unité FCC (CU FCC) kg/s 48,08 48,08 Recycle d'hydrocarbures RA % charge fraîche 27,14 27,14 C/O RA - 6,33 6,87 T sortie RA (ROT) °C 516 516 T charge fraîche RA °C 174 174 Trecyle RA °C 178 178 T REG1 °C 692 686 T REG2 °C 778 757 air utilisé pour la régénération t/h 173,5 194,1 Proportion (air regl)/(air total) % 65,7 61,2 C/O RD - - 14,95 T sortie RD °C - 620 T charge RD °C - 35 Rendements gaz secs % CU FCC 4,77 4,94 Propane % CU FCC 0,95 1,25 Propylene % CU FCC 4,31 6,61 coupe C3 (propane + propylène) % CU FCC 5,26 7,86 coupe C4 % CU FCC 6,61 8,08 Essence % CU FCC 42,72 39,51 LCO % CU FCC 22,48 21,38 Slurry % CU FCC 10,03 9,24 Coke % CU FCC 8,13 8,99 % CU FCC 100,0 100,0 Conversion % 67,49 69,38 We notice :

• RA = riser reactor (residence time: 1 s)
• RD = downstream reactor (residence time: 0.4s)
• REG1 = first regeneration chamber
• REG2 = second regeneration chamber

RA alone RA + RD FCC Unit Charge (CU FCC) kg / s 48.08 48.08 RA hydrocarbon recycle % fresh load 27.14 27.14 C / O RA - 6.33 6.87 T output RA (ROT) ° C 516 516 T fresh charge RA ° C 174 174 Trecyle RA ° C 178 178 T REG1 ° C 692 686 T REG2 ° C 778 757 air used for regeneration t / h 173.5 194.1 Proportion (air regl) / (total air) % 65.7 61.2 C / O RD - - 14.95 T output RD ° C - 620 T charge RD ° C - 35 returns dry gases % CU FCC 4.77 4.94 Propane % CU FCC 0.95 1.25 propylene % CU FCC 4.31 6.61 C3 cut (propane + propylene) % CU FCC 5.26 7.86 C4 cut % CU FCC 6.61 8.08 gasoline % CU FCC 42.72 39.51 OCH % CU FCC 22.48 21.38 slurry % CU FCC 10.03 9.24 Coke % CU FCC 8.13 8.99 % CU FCC 100.0 100.0 Conversion % 67.49 69.38

It is found that propylene can be produced in a substantial amount (53% more) by a really severe cracking dropper, while maintaining a satisfactory gasoline yield. In addition, the temperature the second regenerator dropped by 21 ° C (catcooler effect). A gain in conversion of fresh feed of 1.9% is obtained by depletion of LCO and slurry.

Example 2

In this second example, 99.7% weight of the HCO (or slurry) cut, ie 10% by weight relative to the fresh feed, is recycled as a filler in the dropper.

The conditions are maintained at riser (ROT and recycle) by increasing the C / O of the riser.

We notice :
RA = upstream reactor
RD = downstream reactor
REG1 = first regeneration chamber
REG2 = second regeneration chamber RA RA + RD FCC Unit Charge (CU FCC) kg / s 48.08 48.08 RA hydrocarbon recycle % fresh load 27.14 27.14 C / O RA - 6.33 6.60 T output RA (ROT) ° C 516 516 T fresh charge RA ° C 174 174 Trecycle RA ° C 178 178 T REG 1 ° C 692 689 T REG2 ° C 778 767 air used for regeneration t / h 173.5 190.1 Proportion (air regl) / (air) % 65.7 61.4 total) C / O RD - - 9.7 T output RD ° C - 603 T charge RD ° C - 180 returns dry gases % CU FCC 4.77 4.98 Propane % CU FCC 0.95 1.10 propylene % CU FCC 4.31 4.85 C3 cut (propane + propylene) % CU FCC 5.26 5.95 C4 cut % CU FCC 6.61 7.48 gasoline % CU FCC 42.72 45.07 OCH % CU FCC 22.48 23.44 slurry % CU FCC 10.03 4.27 Coke % CU FCC 8.13 8.81 % CU FCC 100.0 100.0 Conversion % 67.49 72.29

It is found that the HCO (slurry) can be converted substantially (57% conversion) by a really severe cracking dropper, while maintaining a global coke yield of the unit rather low, In addition, the temperature the second regenerator dropped by 11 ° C (catcooler effect), We obtain a gain in conversion of the fresh load of 4.8% by exhaustion of the slurry, leading to better yields of recoverable products (more than 1.5% of LPG and 2.3% more gasoline),

Claims (16)

1. A process for entrained bed or fluidised bed catalytic cracking of at least one hydrocarbon feed in at least two reaction zones, at least one (30) being a riser,
   with the following operating conditions:

   outlet temperature: 500-550°C

   catalyst/feed ratio (C/O) 4-9

   residence time: 0.5-4s

   into which the feed (31) and catalyst (35) from at least one regeneration zone (3) are introduced into the lower portion of the riser reaction zone, the feed and catalyst are circulated from bottom to top in said zone, the first gases produced are separated from the coked catalyst in a first separation zone (38), the catalyst is stripped (40) using a stripping gas, a first cracking and stripping effluent (42) is recovered and the coked catalyst is recycled to the regeneration zone and at least a portion thereof is regenerated using an oxygen-containing gas, the process being characterized in that catalyst (12) from at least one regeneration zone (13) and a hydrocarbon feed (19) are introduced into the upper portion of at least one dropper reaction zone (16), with the following operating conditions:

   outlet temperature: 560°C-620°C
   catalyst/feed ( C/O) ratio: 8-20
   residence time: 0.1-2s
   the catalyst and said feed are circulated from top to bottom under suitable conditions, the coked catalyst is separated from the second gases produced in a second separation zone (20), the second gases produced (24) are recovered and the coked catalyst is recycled (25) to the regeneration zone.
2. A process according to claim 1, in which the operating conditions are the following:

   in the rising zone (RA): catalyst/feed ( C/O) ratio: 5-7

   in the dropping zone (RD): catalyst/feed (C/O) ratio: 10-15
3. A process according to claim 1 or claim 2, in which the catalyst from the second separation zone is stripped using a stripping gas.
4. A process according to claim 1 or claim 2, in which the catalyst is regenerated in two consecutive regeneration zones, the catalyst to be regenerated from the first separation zone is introduced into a first regeneration zone operating at a suitable temperature, the at least partially regenerated catalyst then being sent to the second regeneration zone operating at a higher temperature and the regenerated catalyst from the second regeneration zone is introduced into the riser reaction zone and into the dropper reaction zone.
5. A process according to claim 4, in which the catalyst from the second separation zone is recycled to the first regeneration zone.
6. A process according to claim 5, in which the catalyst is recycled into the dense zone of the first regeneration zone.
7. A process according to claim 5, in which the catalyst is recycled into the dilute zone of the first regeneration zone using a lift.
8. A process according to claim 4, in which the catalyst from the second separation zone is recycled into the second regeneration zone using a lift.
9. A process according to any one of claims 1 to 8, in which the feeds are introduced into the riser reaction zone and into the dropper reaction zone by injection counter-current to the catalyst flow.
10. A process according to any one of claims 1 to 9, in which the feed supplying each of the reaction zones is an uncracked feed termed a fresh feed, a recycle of a portion of the products from downstream fractionation, or a mixture of the two.
11. A process according to claim 10, in which the feed for the riser reaction zone is a vacuum distillate or an atmospheric residue or a recycle of a portion of the products from downstream fractionation and in which the feed for the dropper zone is an uncracked feed or a recycle of a portion of the products from downstream fractionation, preferably of a gasoline cut or an LCO cut.
12. An apparatus for carrying on the process according to any one of the preceding claims said apparatus being in entrained or fluidized bed , comprising:

    • at least one substantially vertical riser reactor (30) having a lower inlet and an upper outlet;

    • a first means (35) for supplying regenerated catalyst connected to at least one regenerator (3) for coked catalyst and connected to said lower inlet;

    • a first means (31) for supplying feed located above the lower inlet of the riser reactor;

    • a first chamber (38) for separating coked catalyst from a first gas phase connected to the upper outlet from the riser reactor (30), said separation chamber comprising a chamber (40) for stripping catalyst and having an upper outlet for a gas phase and a lower outlet for coked and stripped catalyst, said lower outlet being connected to the catalyst regenerator via first catalyst recycling means (45);
    the apparatus being characterized in that it comprises:

    • at least one substantially vertical dropper reactor (16) having an upper inlet and a lower outlet;

    • a second means (12) for supplying regenerated catalyst connected to said coked catalyst regenerator (3) and connected to said upper inlet of the dropper reactor;

    • a second means (19) for supplying feed disposed below the second supply means (12);

    • a second chamber (20) for separating coked catalyst from a second gas phase connected to the lower outlet from the dropper reactor and having an outlet for the second gas phase and an outlet for coked catalyst;

    • and second means (25) for recycling coked catalyst connected to said catalyst outlet from the second separation means and connected to the regenerator.
13. An apparatus according to claim 12, in which the second separation chamber comprises a catalyst stripping chamber communicating therewith.
14. An apparatus according to claim 12 or claim 13, comprising two consecutive coked catalyst regenerators (2,3), and means for circulating the catalyst from the first regenerator (2) to the second regenerator (3), characterized in that said first and second catalyst supply means (35, 12) are connected to the second regenerator (3) and in that said lower outlet from the first separation chamber is connected to the first regenerator via first recycling means (45).
15. An apparatus according to claim 14, in which the second recycling means (2, 5) comprise a lift (29) connected to the second regenerator.
16. An apparatus according to any one of claims 12 to 15, in which the first and second catalyst recycling means each comprise a flow regulating valve (27, 36) controlled by means for measuring the temperature of the catalyst at the outlet of the riser reactor and of the dropper reactor.

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