EP0272973A1 - Process and apparatus for the catalytic cracking of a hydrocarbonaceous food in a reaction zone in which circulate substantially inert and catalytic particles - Google Patents

Abstract

According to the process, the feedstock and a first mixture of a major part of substantially inert solid particles originating from the line (4) are introduced into a vaporisation zone (1a) at a temperature T'2 of between 650 DEG C and 1200 DEG C, the feedstock and the first mixture of solid particles are caused to flow into a stream of carrier gas and a second stage of a major part of catalyst particles of smaller particle size and lower density originating from the line (6) is introduced into a cracking zone (1b) continuous with the vaporisation zone, at a temperature T'1 of between 300 and 750 DEG C, lower than T'2; the resulting mixture is circulated countercurrentwise in the cracking zone (1b), the cracking effluents and the solid and catalyst particles are recovered (9), the said effluents are separated from the said particles, the said particles are separated off (13a) and regenerated, an inert solid particle fraction and a catalyst particle fraction are recovered separately and are recycled into the vaporisation zone and into the cracking zone respectively. Application in the oil industry. <IMAGE>

Description

The invention relates to a process for catalytic cracking of a hydrocarbon feedstock containing residual materials, in a reaction zone in which particles of pretreatment solids and catalytic particles circulate, the apparatus for carrying out the process and its use.

The recovery of heavy loads, commonly called residues (for example atmospheric residue, vacuum residue, deasphalted oils, coal liquefaction oils, shale oils, etc.), by means of catalytic cracking, requires modifications to the tanker. of its refining tools and for example, a pretreatment consisting in particular of removing as much residual materials as possible, such as coke, sulfur and metals, poisons from the catalyst.

When the load to be treated has maximum contents of Conradson Carbon (CCR) and metals respectively of 6-8% and 20-30 ppm by weight, the application of processes of the FCC type (Fluid Catalytic Cracking) is perfectly conceivable. On the other hand, if this charge is heavier (for example CCR> 10%) and especially if the amount of nickel and vanadium reaches several hundred ppm, the pretreatment is necessary, taking into account the performances of the catalysts currently available on the market. Several pretreatment techniques exist, these are in particular delayed coking, fluid coking, hydrotreating, deasphalting, etc.

The prior art is illustrated in particular by the documents below:
. patent EP 127,285 relates to a cracking process in which the charge is vaporized upstream of a reaction column by bringing a conventional cracking catalyst into contact and small quantities of another catalyst are introduced downstream, a ZSM5 zeolite, at a lower temperature to increase the octane number of the gasolines obtained by the conventional catalyst,
. US Pat. No. 3,380,911 describes a process for cracking a charge in which one vaporizes in part and one partially converts this charge by bringing into contact with catalytic particles of small particle size, very active and at low temperature, at the base. of the reaction column. Then vaporized and the rest of the charge is converted, downstream, by catalytic particles of large particle size, of low activity and at higher temperature,
. Finally, it is known in US Pat. No. 4,243,514 to carry out a pretreatment of the charge in an enclosure reserved for this purpose, by vaporizing the charge by mixing with particles of inert solids previously heated. These particles have dimensions between 20 and 150 micrometers (20 - 150 x 10 ⁻⁶ m) and are generated directly in the regenerator by spraying clay mud for example. The microspheres obtained are characterized by their low specific surface which makes it possible to limit the conversion rate to a low level. Nevertheless, they make it possible to capture 95% of the metals and substantially all of the asphaltenes initially contained in the charge. However, the released effluents constituting a satisfactory charge of catalytic cracking in a fluidized bed (FCC) must be cooled before being led to a catalytic cracking zone separate and distant from that where the pretreatment took place, in order to minimize the risks of thermal cracking which would not fail to occur due to long journeys and therefore a long residence time at a high temperature. This would then result in a conversion where the formation of coke would be favored.

It is therefore an object of the invention to pretreat a hydrocarbon feed by subjecting it to contact with particles of previously heated solids, which in particular provide extensive demetallization and substantial elimination of the potential coke contained in the feed during residence times which do not substantially cause thermal cracking.

In conventional cracking processes where the energy necessary for the vaporization of the charge is provided by the catalyst itself, the maximum admissible temperatures for the heated catalyst are of the order of 800 ° C. Beyond that, an accelerated deactivation of the catalyst is observed, especially when its regeneration results in the release of large quantities of water.

An object of the invention is to be able to raise the admission temperature of the particles of heat-transferable solids up to approximately 1200 ° C., in particular in the presence of very asphaltenic fillers, in order to produce a thermal flash of the more intense charge without prejudice to the heat transfer particles which have substantially no catalytic activity.

Another object of the invention is to reduce the aging of the catalyst during the step of cracking the charge which is freed from its heaviest products, to reduce the deactivation of the catalyst and consequently to reduce consumption of catalyst.

Furthermore, in general, high local catalyst / oil ratios in the vaporization zone due to poor distribution of the charge in the injection zone, local temperatures of the vaporized charge greater than 550-600 ° C. in the presence of catalyst and the existence of heterogeneities on a microscopic scale are factors inducing the appearance of significant quantities of residual coke.

Another object of the invention is therefore to ensure a uniform and homogeneous distribution of the charge vaporized in the cracking zone and to minimize the formation of residual coke.

Another object of the invention is to obtain a better and more selective charge conversion resulting in an increase in its recoverable fraction.

In addition, during the cracking of heavy loads in the presence of the only catalyst, there is revealed too much coke, which once oxidized during the regeneration of the catalyst, generates an amount of energy exceeding the energy requirements of the process. Another object of the invention is therefore to adjust the quantity of coke strictly necessary to the needs of the installations (vaporization and cracking of the charge).

By the term of charge, is meant conventional fillers, that is to say distillates having for example final boiling points of the order of 400 ° C., such as gas oils under vacuum, but also oils heavier hydrocarbons, such as crude and / or stripped oils, and residues from atmospheric distillation or vacuum distillation; these charges may, where appropriate, have received a preliminary treatment such as, for example, a hydrotreatment in the presence for example of catalysts of the cobalt-molybdenum or nickel-molybdenum type. The preferred fillers of the invention will be those which may contain high percentages of asphaltenic materials, and which may generally have a high Conradson carbon content, for example greater than 8%, advantageously between 8 and 40%, and preferably between 10 and 25% (see standard ASTM Test 189-65).

These charges can be diluted or not by conventional lighter cuts, which may include cuts of hydrocarbons having already undergone the cracking operation, which are recycled, such as for example light recycling oils ("light cycle oils", LCO ) or heavy recycling oils (HCO). According to a preferred embodiment of the invention, these charges are preheated in a temperature range between 100 and 450 ° C before their treatment.

The invention solves the above drawbacks, and responds to the problems posed by proposing a process for catalytic cracking of a hydrocarbon feed containing residual materials, in a reaction zone in a fluid or entrained bed, characterized in that one introduces into a first portion of the reaction zone called the vaporization zone, said charge, a carrier gas and a first mixture of a major portion of particles of substantially inert solids and a minor portion of catalytic particles distinct from the particles of substantially inert solids, at a temperature Tʹ₂ between 650 ° C and 1200 ° C and preferably between 750 and 1000 ° C, said particles of substantially inert solids having a cracking activity at most equal to about 15%, a particle size between 100 and 2000 micrometers (100 -2000 x 10⁻⁶ m) and a density between 2000 kg / m3 and 6000 kg / m3 and said catalytic particles having a higher cracking activity less than 20%, a particle size between 10 and 100 micrometers (10-100x10⁻⁶ m) and a density between 600 kg / m3 and 1800 kg / m3. Preferably, said first mixture of particles with the charge and the carrier gas is made to flow co-current through said first portion of the reaction zone, so as to vaporize substantially all of the charge and to rid it of at least one part of the residual materials under minimum cracking conditions. The total effluent from the first portion of the reaction zone is introduced into a second portion of the said zone, continues to the said first portion and called the cracking zone, a second mixture of a major part of catalytic particles and a minor part of particles of substantially inert solids, defined above, said second mixture being introduced at a temperature Tʹ₁ lower than said temperature Tʹ₂ and between 300 ° C and 750 ° C, advantageously between 500 ° C and 750 ° C, and preferably between 500 and 650 ° C. The mixture of said total effluent from the first portion of the reaction zone with said second mixture of particles is circulated co-current in said cracking zone , we recover cracking effluents on the one hand and solid particles and catalytic particles on the other hand, which contain at least partially a cracking residue, the cracking effluents are separated from the solid particles and catalytic particles. Said solid and catalytic particles resulting from the step of separating said effluents are subjected to at least one step for separating the particles and at least one step for regeneration in a fluidized or entrained bed and a fraction containing the major part of the particles is recovered separately. solid particles and a fraction containing the major part of the catalytic particles and at least partly recycling said solid particles in the vaporization zone and said catalytic particles in the cracking zone of said reaction zone.

The catalytic particles are, of course, solid particles, but active. To differentiate them from particles of substantially inert solids, or will call them for convenience catalytic particles or catalyst. The temperature Tʹ₁ for introducing the catalytic particles is advantageously at least 10 ° C lower than the temperature Tʹ₂ for introducing the particles of substantially inert solids.

The method according to the invention has the advantage of carrying out in a very short time the vaporization of the charge and the elimination of impurities, substantially reducing the thermal cracking and therefore the preferential formation of coke. Furthermore, the quantity of coke deposited on inert particles during the vaporization stage of the feedstock is less compared to that deposited on a conventional cracking catalyst under the same temperature conditions. The charge vaporized on contact with the solid particles is made acceptable for the catalytic cracking catalyst. It is in fact advantageously freed, for example, of at least 90% of the residual materials, thus ensuring a longer service life for the catalyst and slower deactivation of its sites. active during the regeneration of said catalyst. Catalytic and thermal cracking in the vaporization zone is also minimized, which avoids the formation of coke and ensures better conversion.

The existence of heterogeneities in the vaporization zone is reduced and a uniform and homogeneous distribution of the charge in the vaporization zone where mainly the particles of substantially inert solids circulate, is ensured, which minimizes the formation of coke. thermal origin. Furthermore, the conversion is better and more selective since the actual cracking takes place in an atmosphere of gaseous hydrogen-donating hydrocarbons.

Finally, the hydrocarbon vapors of the feed can be brought into contact with the catalyst at a lower temperature than that usually encountered in catalytic cracking processes since this catalyst must only provide the heat absorbed by the cracking, heat which represents only about 10 to 20% of the heat of vaporization of the charge. This feature can help minimize the amount of residual coke and cracking. On the other hand, the lifetime of the catalyst is thereby increased and its activation level maintained longer.

According to a particular embodiment of the invention, the vaporization (and pre-treatment) zone can have a length L and an internal diameter D such that the ratio L / D is between 2 and 30 and preferably between 5 and 15 , which facilitates a homogeneous distribution of the charge and a substantially complete vaporization of the latter before it reaches the cracking zone supplied with catalytic particles.

The distance separating the introduction of the two distinct populations of particles therefore depends on the diameter of the reaction zone where the charge is vaporized. In the preferred conditions of the L / D ratio, it is possible to vaporize substantially all of the charge without substantial cracking in the vaporization zone, to deposit almost all of the residual coke and of the metals on the solid particles, and to generate substantially only the minimum of coke necessary for the operation of the unit, according to the process. The installations are all the more simplified since the thermal levels are lowered and their investment cost reduced.

The solid particles are distinguished from the catalytic particles not only by their activity, but especially by their size and their density, which promotes their separation thereafter.

Indeed, the particles of pretreatment solids generally have a specific surface of less than 50 m² / g, for example between 0.01 and 50 m² / g (so-called BET method using nitrogen absorption), preferably included between 0.01 and 20 m² / g and even more preferably, between 0.01 and 10 m² / g, which contributes to minimizing the thermal cracking of the load. They have a size varying from 100 to 2000 micrometers (100 to 2000 x 10⁻⁶ m) and preferably from 200 to 300 micrometers (200 to 300 x 10⁻⁶ m). Their density is between 2000 and 6000 kg / m³ and advantageously between 2500 and 5000 kg / m³. These microspheres have a low catalytic activity and are of low cost. The activity is defined as being the ratio of the conversion rate obtained in the presence of the solid particles considered, on the conversion rate obtained in the presence of the reference catalyst, within the framework of standardized MAT tests (Standard ASTM D 3907-80) . For example, during MAT tests, sand particles with a specific surface area of less than 1 m² / g lead to conversion rates of around 7.3% with a filler constituted by an Arabian light residue, characterized by a 5.0% Conradson carbon. The tests were carried out at 530 ° C with a C / O ratio of 4.5. This conversion rate is to be compared with that of 71% obtained under the same conditions procedures with a conventional catalyst based on faujasite (zeolite Y) and a specific surface area equal to 91 m² / g. The conversion rate is defined as the ratio: mass (gas + petrol + coke) / mass of the initial charge. It is therefore recommended because of their low cost to reject some of these particles of solids from time to time and replace them with the same amount fresher, so as to maintain an acceptable metal content. Indeed, their analysis shows that they contain, in addition to minerals, silica, alumina and small amounts of impurities in the form of titanium, iron and alkaline earth. The solid particles used are, for example, calcite, dolomite, limestone, bauxite, baryte, chromite, zirconia, magnesia, perlite, alumina and silica, all these solid particles having a low specific surface.

On the other hand, the catalysts are generally those used and described in the catalytic cracking processes; zeolite-based catalysts are often preferred and among these, those which exhibit good thermal stability in the presence of water vapor. They have an average particle size equal to 50 micrometers (50 x 10⁻⁶ m) which is distributed between 10 and 100 micrometers, advantageously between 30 and 70 micrometers. Their specific mass is between 600 and 1800 kg / m³ and preferably between 800 and 1600 kg / m³.

The separation and regeneration of all the particles can be carried out in different enclosures or in the same enclosure. The relative contents of particles of the different types in the reaction zone will be a function of the mass flow rates of particles introduced into the vaporization zone and into the cracking zone.

Generally, the ratio of the mass flow rate of particles introduced into the vaporization zone to the mass flow rate of particles introduced into the cracking zone is between 1 and 100, advantageously between 1 and 10 and preferably advantageously between 1 and 1.5. The mass percentage of catalytic particles present in the first mixture and entrained with the solid particles during the separation and / or regeneration stages, which arrive in the vaporization zone is for example between 0.2 and 10%, advantageously between 1 and 5%, so that there is substantially no cracking.

In the second mixture comprising the major part of the catalytic particles introduced into the cracking zone, we will find in particular a part of the particles of very fine inert solids resulting from the attrition of the particles of inert solids and therefore the proportion of the inert particles present in the second mixture is necessarily a function of the ratio of the flow rates of the first and of the second mixture. For example, the proportion of inert particles in the second mixture will be higher the greater the ratio of the mass flow rate of the first mixture to the mass flow rate of the second mixture.

The mass percentage of the inert particles in the second mixture introduced into the cracking zone is between 1 and 40% and advantageously between about 2 and 10%, the rest at 100% obviously corresponding to the catalytic particles.

Taking into account the advantageous and preferred values above, the particles of inert solids in the cracking zone proper can represent from 45 to 94.4% by weight and advantageously from 45 to 75% by weight of the resulting mixture corresponding to the total effluent. leaving the vaporization zone and at the second mixture of particles while the catalytic particles can represent from 4.6 to 55% by weight of the resulting mixture and preferably from 25 to 55% by weight.

According to a first embodiment of the particularly advantageous method, in particular in engineering (see FIG. 1 below), the particles of inert solids can be regenerated and catalytic in the same area, substantially at the same time as the step of separating the two types of particles. This regeneration step can generally be carried out in the presence of oxygen or of a gas comprising molecular oxygen at a temperature T₂ of between 650 ° C and 1200 ° C and at a fluidization speed of between 0.1 m / s and 2 m / s. Under these regeneration conditions, it is possible to cause the combustion of at least 90% of the residual materials present on the solid particles and at least for example 70% of cracking residues and of residual materials which are fixed on the particles. catalytic.

It is possible, according to another embodiment of the invention, to subject the fraction enriched in catalytic particles to a second regeneration at a temperature T₁ of between 500 and 750 ° C. in a second regeneration zone in communication with the first zone, by means of a gas comprising molecular oxygen, the temperature T₁ being lower than the temperature T₂, advantageously at least 10 ° C. This second regeneration makes it possible to perfect the regeneration of the catalytic particles since at least 90% of the residual materials and / or the cracking residues are oxidized.

According to a second embodiment of the method (see FIG. 2 below), the step of separating the two types of particles can be carried out in an enclosure then the step of regenerating the particles in two separate enclosures, one reserved for the regeneration of solid particles at the conditions of temperature T₂ and speed of fluidization expressed above, the other reserved for the regeneration of catalytic particles at the conditions of temperature T₁ and speed expressed above.

Spraying or atomizing means can introduce the charge at a speed preferably between 10 and 100 m / s. Generally the carrier gas stream is adapted to generate a particle speed of approximately 2 to 10 m / s and the charge and the solid particles are generally left in contact between approximately 400 ° C. and 650 ° C. for a residence time. of the charge in the vaporization zone of between 0.01 s and 2 s approximately.

The invention also relates to a catalytic cracking device for implementing the process (see fig. 1), it comprises:
- a reactor (1) which is a pipe of elongated tubular shape and substantially vertical, comprising a vaporization zone 1a of length L and internal diameter D such that the ratio L / D is between 2 and 30 and a cracking zone 1b continues at said vaporization zone,
- inlet means (3) for a liquid or gaseous charge connected to the end of said reactor in the vaporization zone (1a) and containing means for spraying or atomizing said charge in said reactor, which confer charge flow from top to bottom, or from bottom to top in the reactor,
- input means (4) of mainly solid particles, connected to said end of the reactor, in the vaporization zone (1a) and giving these solid particles a flow movement directed from top to bottom or from bottom to top in the reactor,
- input means (6) of mainly catalytic particles in the cracking zone (1b) of said reactor 1, connected to said reactor 1 downstream of the input means (4) of particles mainly of solids, said inlet means (6) being adapted to produce a flow of said mainly catalytic particles in the direction of flow of the solid particles and of the charge,
- means of separation by stripping (8, 9, 10) of the cracking reaction effluent and of the solid and catalytic particles connected to said reactor, at the end opposite to that where said load input means (3) are connected,
- outlet means (22) of the reaction effluent connected to said separation means (8, 9, 10),
- means of transport (12) of solid and catalytic particles, either to at least one means of separation and regeneration (13a) of solid particles and catalytic particles then to at least one storage enclosure (13b) of the particles catalytic at least partially regenerated either towards at least one means of separation (26 fig. 2) of the solid particles from the catalytic particles then towards at least one means of regeneration of the solid particles (30 fig. 2) and at least one means regeneration of catalytic particles (28 fig. 2),
- either gas-particle separation means and smoke outlet (14,21) connected to the regeneration means (13a),
either gas-particle separation means and smoke outlet (fig. 2, 34 and 36, 35 and 37) connected respectively to said means for regenerating catalytic particles (28 fig. 2) and to said means for regenerating solid particles ( 30, fig. 2).
- recycling means (7, 23, 46) of particles which are mainly catalytic at least partly towards said inlet means (6), said recycling means (23) being connected either to the storage enclosure (13b ) either by means of regeneration (28), and
means for recycling (5,16,45) particles mainly of solids at least in part towards said inlet means (4), the recycling means (16) being connected either to the first regenerator (13a), either to said regeneration means (30).

The apparatus is therefore very compact and has the advantage of combining in a single enclosure two functions, one for spraying and pretreatment, the other for cracking, and therefore to achieve engineering savings.

The invention will be better understood, in view of FIG. 1 presented below schematically representing a particular embodiment of the apparatus with an ascending reaction zone, at the lower end of which the charge is introduced and in view of the FIG. 2 illustrating a separation zone and two distinct regeneration zones for the two types of particles.

According to FIG. 1, the reaction zone or reactor 1 is an elongated and substantially vertical tubular pipe. It comprises a lower part or vaporization zone 1a and an upper part or catalytic cracking zone 1b continues at the vaporization zone. The charge to be cracked, which can be heated beforehand between 100 and 450 ° C., is supplied by at least one line 3.

Known spray means such as those described in US Patent ^No. 4,331,533 introduces the feed to the bottom of the evaporation zone, preferably above the arrival of the solid particles (4) to a speed for example of around 100 m / s.

The load is brought into contact with these particles mainly comprising particles of inert solids (for example at least 95%), which may be, by way of illustrative example, zirconia with an average particle size of between 200 and 300 micrometers and of density between 2000 and 6000 kg / m³ and activity equal to approximately 10%, and which are introduced through line 16 by the inlet means 4 at a flow rate controlled by the valve 5 and at a speed for example about 3 m / s at a temperature Tʹ₂ between 650 ° C and 1200 ° C, for example at 800 ° C. The solid particles and the charge flow into the vaporization zone 1a.

The injection 60 of steam and light hydrocarbons 30 of 1 to 5 carbon atoms as carrier gas for solid particles makes it possible to dilute the vapors obtained, thus reducing the reactions of condensation and above all to operate the vaporization in a hydrogenating atmosphere thus resulting in an increase in the recoverable fraction of the charge, therefore a better conversion, all the more since the presence of special devices (fluidized siphons 45, 46, 47) isolates the different atmospheres of the general apparatus.

The vapors formed in the vaporization zone 1a of the reactor 1 leave this zone 1a after a residence time of 0.5 s. approximately and are brought into contact in the cracking zone 1b continues at the vaporization zone 1a with particles mainly catalytic (for example at least 80%), of particle size ranging for example between 30 and 70 micrometers and density varying by example between 900 and 1400 kg / m³. A line 23 brings these particles by inlet means 6 to the base of the cracking zone 1b, that is to say to the upper part of the vaporization zone, at a speed for example of around 1, 5 m / s and at a temperature Tʹ₁ <Tʹ₂ advantageously between 500 ° C and 750 ° C, for example at 650 ° C. The flow of catalyst is controlled by the valve 7. A heat exchanger (not shown in the figure) can be fitted on the line 23 upstream of the valve 7 to cool the catalytic particles coming from the storage area 13b. The temperature of the vaporization zone is generally between 400 ° C and 600 ° C, for example between 450 and 600 ° C while the temperature of the cracking zone is for example between 450 and 600 ° C.

At least one constriction 2 advantageously located in the upper part of the vaporization zone between the means for entering the particles 4 and 6 locally creates high speeds, which limits the fall of catalyst in part 1a. These high speeds are also intended to create significant turbulence at the level of bringing the hydrocarbon vapors into contact with the catalyst and thus ensuring an intimate mixture of the two phases.

The vaporization zone 1a, of length L is defined from the lower part of zone 1a to the neck of the constriction 2 situated between the convergent of zone 1a below the neck and the diverging of zone 1b to above the collar. It is mainly at the level of the convergent and the neck that the inert particles are accelerated.

Good results have been observed with an opening angle of the convergent between 5 and 50 degrees, preferably between 5 and 20 degrees, with an opening angle of the diverging between 20 and 180 degrees. The ratio of the diameter of the neck to the diameter of the vaporization zone is generally between 0.25 and 1 and preferably between 0.6 and 0.8. It has been observed that with these preferred values, weeping was obtained through the neck of between 0.1 and 2% of the total flow rate of catalyst injected into the cracking zone.

The vaporization zone 1a defined by its distance L and its diameter D is such that the ratio L / D is between 2 and 30 and advantageously, between 5 and 15. In the cracking zone 1b of the reactor 1 circulates l effluent comprising the solid particles charged at least in part with the residual materials, the vaporized charge and the catalytic particles. The residence time of the charge in the vaporization zone generally does not exceed 1000 ms and preferably remains less than 500 ms while the residence time of the vaporized charge in the cracking zone 1b is approximately 0.01 seconds. about 2 seconds and preferably about 0.2 s to 1 second. At the outlet of the reactor, in an enclosure 9 constituting a means of separation by stripping of the hydrocarbons adsorbed on the catalyst, by means of steam supplied by a line 11, a ballistic separator 8 provides a first separation of the gaseous effluents and of the particles.

The cracking effluents leave the enclosure 9 via a pipe 22 after passing through at least one cyclone 10, while the mixture of particles is sent to the first regenerator 13a by the transport line 12, a valve 48 of which controls the debit.

The inert solid particles and the catalyst arrive in the enclosure 13a where the separation of the two populations of particles is carried out simultaneously, as a function of their size and their mass, the regeneration of the catalyst as well as the oxidation of the coke deposited on the inert solid particles. This enclosure 13a comprises at least two compartments 50 adapted to create different thermal levels and the last of which ensures the storage of inert particles. The compartmentalization is carried out by means of walls for example of refractory plates 15 placed in a substantially perpendicular manner on the base of the enclosure. The solid particles thus flow in cascade from the compartment supplied by the line 12 equipped with a valve 48 and a fluidized siphon 47 to the compartment where the inert solid particles are extracted by a line 16 provided with a valve 5 and a fluidized siphon 48 which transfers the particles of inert solids to the vaporization zone 1a of the reactor. A compressor 17 supplies oxidizing gas (air for example) via a line 20a to at least one diffuser 19 of the regenerator 13a. In each compartment, only part of the air necessary for the complete oxidation of the coke deposited on the inert particles and for the regeneration of the catalyst is introduced. In this way, the temperature of the inert solid particles rises in stages to the point of extraction (end of the line 16 in the enclosure 13a). The operating conditions (that is to say mainly the fluidization speed) are adjusted so as to have a substantial entrainment of the catalyst in the first compartments in order to avoid any stay of the catalyst at high temperature, which would harm its activity and accelerate its aging. The temperature profile in the regenerator is adjusted so that the average temperature of the entrained catalyst is substantially close to the reinjection temperature in the cracking zone 1b. A second compartmentalization can be carried out with walls 15a, for example plates suspended from the ceiling of the enclosure 13a and plunging into each fluidized compartment 50 and makes it possible to isolate the gaseous atmospheres surmounting each of the compartments. defined by the walls 15a, thus avoiding a mixture of the catalyst particles entrained above each of the compartments. This compartmentalisation also makes it possible to recover, on the one hand, combustible regeneration effluents above the compartments operating at low temperature and lacking oxygen or air, and non-combustible regeneration effluents above the compartment or compartments. operating at high temperature where the extraction of inert solid particles takes place. The problems posed by the post-combustion of carbon monoxide in the space above the particle beds are also avoided, since a reducing zone (compartment (s) 50 at low temperature) can be separated from an oxidizing zone ( compartment (s) 50 at high temperature). The regeneration effluents pass through cyclones 14 and are evacuated via line 21.

The particles of catalyst captured by at least one cyclone 14 placed in each of the spaces defined by the walls 15a are directed towards a storage enclosure 13-b operating in a fluidized bed and supplying the cracking zone 1b equipped with a valve 7 and d 'a fluidized siphon 46 via the line 23. This enclosure 13b may also comprise, according to another embodiment, additional regeneration means if the regeneration has proved insufficient at the level of the enclosure 13a. Furthermore, to reinforce the difference between the temperatures Tʹ₁ and Tʹ₂ of the two populations of particles, it is possible to envisage preheating the combustion air (oxidizing gas) of the hot compartments of the enclosure 13a by passing this air through the bed. of catalyst. According to this particular embodiment, the cold air can be introduced by means of the diffuser 24 generally located at the base of the enclosure 13b and supplied by a line 20b connected to the compressor 17, can be heated by crossing the fluidized bed contained in enclosure 13-b, can be freed of particles entrained by cyclones 25 and can finally be introduced into the "hot" compartment (s) of enclosure 13a by diffusers 19.

According to another embodiment, the temperature difference in the two regenerators can be reinforced by any other means, in particular by installing at least one exchange surface, of known type and not shown in the figure, in the catalytic particle regenerator.

According to another mode of operation of the process shown diagrammatically in FIG. 2, it is possible to envisage operating the separation of the two populations of particles in a first step, and then independently, the regeneration of the catalyst and the oxidation of the deposited coke on inert solid particles in a second step.

The mixture of catalyst and inert solid particles arrives via line 12 in an enclosure 26 where the two populations of particles in a fluidized bed are separated. This separation can be carried out by entraining the catalyst above the fluidized bed, by segregation within the fluidized bed itself or by a combination of the two processes. FIG. 2 represents for example a schematic device for separation by entrainment. The entrained catalyst grains are captured by at least one cyclone 27 and directed towards the regenerator 28 by line 29 while the fumes are evacuated by line 27a. The inert solid particles which constitute the fluidized bed, are directed towards the regenerator 30 by the line 31. The separation enclosure 26 can be compartmentalized like the enclosure 13a described previously so as to improve from one compartment to another the separation of the two populations of particles. It is supplied with steam or fumes from one or other of the regenerators 28 or 30. These regenerators 28 and 30 are supplied with air or gas containing oxygen by the lines 32 and 33 respectively. The fumes produced by the regeneration leave the two chambers 28 and 30 by lines 34 and 35 after being dusted by cyclones 36 and 37.

The inert solid particles are heated to a higher thermal level than that of the catalyst because their coke content is greater since they have fixed almost all of the potential coke contained in the charge. To accentuate the temperature difference between the two populations, it is possible, for example, to preheat the air of the regenerator 30 by passing this air through the regenerator 28 through the fluidized bed as has already been described above. The catalyst and the particles of inert solids then return to the reactor 1 via lines 23 and 16 equipped respectively with valves for adjusting the flow rates of particles 7 and 5 and of fluidized siphons 46 and 45.

To maintain the fluidization of both the solid particles and the catalyst, at least one fluidization vapor inlet can be introduced on the various lines, for example the injection 54 on the line 12, the injection 52 on the line 23 and injection 53 on line 16.

The invention has been illustrated by FIG. 1 representing a particular embodiment with an ascending reactor, but it is possible in the same spirit to produce a reactor where the circulation of the types of particles and of the charge is descending.

Claims (14)

1. Process for the catalytic cracking of a hydrocarbon feedstock having a high Conradson carbon value and containing residual materials in a reaction zone in a fluid bed in which two types of particle size different to two are introduced at different temperatures Tʹ₂ and Tʹ₁ different levels of the reaction zone, characterized in that one introduces into a first portion of the reaction zone called the vaporization zone, said charge, a carrier gas and a first mixture of a major portion of particles of substantially inert solids and d '' a minor part of catalytic particles distinct from particles of substantially inert solids, at a temperature Tʹ₂ of between 650 ° C and 1200 ° C, said particles of substantially inert solids having a specific surface of less than 50m² / g, a cracking activity at more equal to about 15%, a particle size between 100 and 2000 micrometers (100-2000 x 10⁻⁶m) and a e density between 2000kg / m³ and 6000kg / m³ and said catalytic particles having a cracking activity greater than 20%, a particle size between 10 and 100 micrometers (10-100 x 10⁻⁶m) and a density between 600kg / m³ and 1800kg / m³, said first portion of the reaction zone is made to flow said first mixture of particles with the charge and the carrier gas, so as to vaporize substantially all of the charge and to rid it of at least one part of the residual materials under minimum cracking conditions, the total effluent from the first portion of the reaction zone is introduced into a second portion of the said zone, continues to the said first portion and called the cracking zone, is introduced simultaneously with the inlet of said second portion a second mixture of a major portion of catalytic particles and a minor portion of substantially inert solid particles defined above, said second mixture was nt introduced at a temperature Tʹ₁ lower than said temperature Tʹ₂ and between 300 and 750 ° C., the mixture of said effluent is circulated cocurrently in said cracking zone total of the first portion of the reaction zone with said second mixture of particles, cracking effluents are recovered on the one hand and solid particles and catalytic particles on the other hand, which contain at least partially a cracking residue , the solid particles and the catalytic particles are separated from the cracking effluents, said effluents are recovered, said solid and catalytic particles resulting from the step of separating said effluents are subjected to at least one step of separation of particles and to minus a regeneration step in a fluidized bed, a fraction containing the major part of the solid particles and a fraction containing the major part of the catalytic particles is recovered separately and said solid particles which are substantially inert in the vaporization zone and said catalytic particles in the cracking zone of said reaction zone. 2. The method of claim 1 wherein the filler and most of the solid particles are introduced at the base of the vaporization zone. 3. Method according to one of claims 1 to 2, in which the solid particles are chosen from the group formed by calcite, dolomite, limestone, bauxite, baryte, chromite, magnesia, perlite, alumina and silica of low specific surface. 4. Method according to one of claims 1 to 3, wherein the vaporization zone has a length L and an internal diameter D such that the ratio L / D is between 2 and 30. 5. Method according to one of claims 1 to 4 wherein the speed of the particles of said first mixture is increased in the upper part of said vaporization zone. 6. Method according to one of claims 1 to 5 wherein said first mixture of particles is introduced into the vaporization zone and said second mixture of particles into the cracking zone under conditions of mass flow ratio and mass percentage such that the proportion of said catalytic particles in the cracking zone represents approximately 4.6 to 55% by weight of the total mixture thus constituted and advantageously from 25 to 55% by weight. 7. A catalytic cracking apparatus for implementing the method according to claim 1 comprising (FIG. 1):
- a reactor (1) which is a pipe of elongated tubular shape and substantially vertical comprising a vaporization zone (1a) of length L and internal diameter D such that the ratio L / D is between 2 and 30 and a zone of cracking (1b) continues at said vaporization zone,
- inlet means (3) for a liquid or gaseous charge connected to the end of said reactor in the vaporization zone (1a) and containing means for spraying said charge into said reactor, which give the charge a flow from top to bottom, or from bottom to top in the reactor,
- input means (4) of solid particles, into the vaporization zone (1a), connected to said end of the reactor and giving these solid particles a flow movement directed upwards or downwards high in the reactor,
- input means (6) of mainly catalytic particles (1) in the cracking zone (1b), connected to said reactor (1) downstream of the input means (4) of particles mainly of solids , said inlet means (6) being adapted to produce a flow of said mainly catalytic particles in the direction of flow of the particles of solids and of the charge,
- means of separation by stripping (8, 9, 10) of the cracking reaction effluent on the one hand and solid and catalytic particles on the other hand, connected to said reactor (1) at the end opposite to that where said load input means (3) are connected,
- outlet means (22) of the reaction effluent connected to said separation means (8, 9, 10),
- means of transport (12) of solid and catalytic particles, either to at least one means of separation and regeneration (13a) of solid particles and catalytic particles then to at least one storage enclosure (13b) of the particles catalytic at least partially regenerated, either towards at least one means of separation (26 fig. 2) of the solid particles from the catalytic particles then towards at least one means of regeneration of the solid particles (30 fig. 2) and at least one means of regeneration of the catalytic particles (28 fig. 2),
- either gas-particle separation means and smoke outlet (14,21) connected to the regeneration means (13a), or gas-particle separation means and smoke outlet (fig. 2, 34, 35, 36 and 37 ) connected respectively to said means for regenerating the catalytic particles (28 fig. 2) and to said means for regenerating solid particles (30, fig. 2),
- recycling means (7, 23, 46) of particles which are mainly catalytic at least in part towards said inlet means (6), said recycling means being connected either to the storage enclosure (13b), or by means of regeneration (28) and
- recycling means (5,16,45) of particles mainly of solids at least partly towards said inlet means (4), the recycling means being connected either to the regenerator (13a), or by means of regeneration (30). 8. Apparatus according to claim 7 wherein the reactor (1) comprises at least one throttle (2) interposed between the inlet means (4) of the solid particles and the inlet means (6) of the catalytic particles, at the upper part of said vaporization zone. 9. Apparatus according to one of claims 7 and 8 wherein the storage enclosure (13b) comprises regeneration means comprising at least at the base of said enclosure at least one supply means (24) in oxidizing gas. 10. Apparatus according to one of claims 7 to 9 wherein the storage enclosure (13b) comprises means for cycloning (25) of the oxidizing gas before it passes through a second supply means (19). 11. Apparatus according to one of claims 7 to 10 wherein the recycling means (5, 16, 45) of the solid particles comprise a valve (5) connected to the inlet means (4) and a fluidized siphon (45 ) interposed between said valve (5) and the regeneration means (13a; fig. 2, 30). 12. Apparatus according to one of claims 7 to 11 wherein the recycling means (7,23,46) of the catalytic particles comprise a valve (7) connected to the inlet means (6) and a fluidized siphon (46) interposed between said valve 7 and either the storage enclosure (13b) or the regeneration means (32 fig.2). 13. Apparatus according to one of claims 7 to 12 wherein the regeneration means (13a) comprises at least two compartments and at least one means for adjusting the fluidization speed in said compartments. 14. Apparatus according to one of claims 7 to 13 wherein the reactor (1) is ascending.

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