WO2020260029A1

WO2020260029A1 - Reactor for the catalytic treatment of hydrocarbons with semi-continuous catalyst replacement

Info

Publication number: WO2020260029A1
Application number: PCT/EP2020/066160
Authority: WO
Inventors: Vincent Coupard; Beatrice Fischer; Nicolas ARIBERT; Stéphane GIRARDON; Eric Sanchez
Original assignee: IFP Energies Nouvelles
Priority date: 2019-06-26
Filing date: 2020-06-11
Publication date: 2020-12-30
Also published as: FR3097779A1

Abstract

The present invention relates to a reactor 1, 2 for the catalytic treatment of hydrocarbons, in particular with radial circulation, comprising a fixed catalyst bed and periodic regeneration of the catalyst in situ, such that the reactor is in fluid connection, on one hand, with a system 31, 32 for the partial loading of fresh catalyst upstream and, on the other hand, with a system 33, 34 for the partial unloading of used catalyst downstream, said systems replacing only a portion of the used catalyst from the reactor with fresh catalyst after at least one, preferably each, regeneration in situ of the catalyst.

Description

Hydrocarbon catalytic treatment reactor with semi-continuous catalyst replacement

Technical area

The invention relates to the catalytic treatment of hydrocarbons. Catalysts are in fact very widely used in refining and petrochemical installations, in processes operating a certain number of reactions in parallel and / or chain on hydrocarbons. Mention may be made of the catalytic reforming process, aimed at converting naphthenic and paraffinic compounds into aromatic compounds, and involving, in particular, the dehydrogenation of naphthenes, the dehydrocyclization of paraffins into aromatics, and isomerization of paraffins and naphthenes. Mention may also be made of the processes of the hydroconversion, hydrocracking, fractionation type, involving a succession of reactions, the fluid catalytic cracking process known by the acronym FCC for the corresponding English term Fluid Catalytic Cracking, or also the reactions of metathesis d. olefins etc ...

Prior art

To carry out all these reactions, there are different families of catalysts. They tend to wear out, deactivate / passivate gradually, which is why they must periodically be replaced with "fresh" catalyst, and / or be regenerated in order to be able to prolong their use. The catalyst is gradually covered with coke over time. When the amount of coke is too large, the operation must be stopped to regenerate the catalyst, usually by burning the coke. Cycle time is the operating time between two regenerations. At each regeneration, due to the high temperatures of the regeneration, the catalyst sintered, that is to say, it loses some active surface. Over the course of regenerations, it therefore loses activity, and after a certain number of regenerations, it is at the end of its life and must be changed. The service life is the total operating time between two catalyst changes, it is equal to the number of regenerations multiplied by the cycle time.

The replacement of the spent catalyst with fresh or regenerated catalyst outside the reactor can be done during periodic production shutdowns of the installation / reactor containing the catalyst, for example during scheduled annual shutdowns of the installation. This is an interesting solution when the lifetime / cycle of the catalyst is long enough to be compatible with a long periodicity, of annual type.

However, in some cases the catalyst does not have a long enough cycle time for this. We must then consider other solutions.

A first solution consists in using a moving bed catalyst technology, with continuous regeneration of the catalyst in a dedicated regeneration reactor in fluid connection with the catalytic treatment reactor (or several treatment reactors in series), as is done in so-called regenerative catalytic reforming units. An example is given in patent FR-3 024 460. This solution also exists for catalytic treatment reactors in catalytic cracking units of the FCC type. It is a powerful solution, but of high technology and therefore quite complex / expensive to implement.

There are other less complex / costly solutions to implement, including a second solution known by the Anglo-Saxon term of "swing", therefore in rocking mode: it consists in using a unit comprising several reactors operating in parallel, some being in operation mode while others are in catalyst regeneration mode, or in standby or catalyst loading mode, with switching from one mode to another by a piloting which can be automatic, in particular at the using appropriate pilot valves. As it is also necessary to change the catalyst after a certain number of regenerations, in practice, for a reactor in production, we can therefore have two reactors (the one in regeneration and the one waiting for catalyst) which do not produce, which does not is not great in terms of productivity. This second solution makes it possible to regenerate catalysts with shorter lifespans / cycles, by dispensing with, for catalyst regeneration, the periodicity imposed by annual plant closures, for example.

However, this second solution is not devoid of drawbacks: in fact, in a given reactor in production mode, the catalyst gradually loses its activity over the regenerations, which means that the operating conditions must be gradually modified in parallel. , in particular by having to increase the reaction temperature to maintain the yields. It also turns out that the selectivity of the desired reactions can change. And when a reactor filled with fresh catalyst is brought into operation mode instead of a reactor full of catalyst at the end of its life, it is necessary again to modify, very quickly this time, the operating conditions in the opposite direction, in particular the temperature. These periodic modifications of the operating conditions and a certain fluctuating nature of the results in terms of composition of the effluent obtained, and of yield, which is difficult to erase completely, are not without risk from an industrial standpoint, more particularly when the effluent from the outlet of the Reactor in production mode is then processed in a downstream distillation column. Indeed, a distillation column subjected to a sudden change in feed composition can go out of adjustment, go into oscillation, and it may take hours before products meet specifications, which can lead to production losses. A first solution consists in providing several reactors in parallel production, operating with different catalyst ages, staggered, from one reactor to another, which makes it possible to homogenize / smooth the characteristics of the overall effluent obtained by averaging the fluctuations in production.

This effective remedy is, however, relatively expensive in terms of equipment, and complex to implement on an industrial scale.

The aim of the invention is therefore to improve the operation of reactors in rocking mode (also called “swing” mode), in particular in order to have more stable operating conditions and / or more homogeneous results (yield, selectivity). throughout a production campaign and / or to facilitate reactor management and / or to have a more productive installation.

Summary of the invention

The subject of the invention is first of all a reactor for the catalytic treatment of hydrocarbons, in particular with radial circulation, comprising a fixed catalyst bed and with periodic regeneration of the catalyst in situ. Said reactor is in fluid connection, on the one hand, upstream, with a system for partially loading fresh catalyst, and, on the other hand, downstream, with a system for partially unloading spent catalyst, said systems replacing a only part of the catalyst spent from the reactor with fresh catalyst after at least one, preferably every, in situ regeneration of the catalyst.

With the invention and its partial catalyst loading and unloading system for each reactor, operation in "swing" mode is greatly improved. With the invention, the plant can operate the reactors in pairwise flip-flop mode only, with one reactor in production for a non-productive / regenerating reactor (without the need for a third non-productive reactor, which was usually in charging mode). catalyst or waiting for the load in question). Indeed, while one of the reactors is in production, the other will be able to switch to regeneration and partial catalyst change mode. This partial change step can be done very quickly, and will preferably affect the portion of catalyst in the reactor which will have undergone the most regenerations, therefore the portion of catalyst that is the most “worn”. This step is enabled by the systems according to the invention.

Taking the example of a catalyst which has a lifespan of 30 days, and in the case where the catalyst in question is regenerated once a day, this means that with the invention we will be able, in the reactor in regeneration, just after its regeneration, change 1/30 ^th of the catalyst contained in the reactor, therefore a small volume, this change being possible quickly and easily thanks to the invention: everything then takes place as if the replacement of the catalyst was done almost continuously, semi-continuously, so that the reactor will permanently contain 1/30 ^th of the catalyst having undergone regeneration, 1/30 ^th of catalyst having undergone two regenerations, etc. Thus, the activity of the catalyst will be, overall, in the reactor, constant over the entire production period. It is then no longer necessary to modify the operating conditions over time, as in the preceding solutions, in order to obtain products of constant quality and yield.

This is a considerable gain in terms of investment and space requirements on an industrial site (fewer reactors immobilized for the same production). It is also a considerable gain in terms of simplifying the maintenance / management of the operating conditions of reactor operation. Finally, it is a gain in terms of consistency in the yield and quality of the products obtained.

A subject of the invention is also the process for using such a reactor.

Preferably, the / each partial loading of fresh catalyst and the / each partial unloading of spent catalyst relates to identical volumes of catalyst: a certain volume of “used” catalyst is therefore removed to replace it with an identical volume (to industrial tolerances. near) "fresh" catalyst, so that the reactor, in production mode, always operates with a constant volume of catalyst.

Preferably, the partial loading of fresh catalyst and the partial unloading of spent catalyst are concomitant: the time required for this double operation can thus be reduced as much as possible.

The partial loading and / or unloading the catalyst part may relate to a volume V1 of catalyst corresponding to between ^1/10 and ^1/200, in particular between 1 / ^20th and 1 / ^100th or 1 / ^30th and 1 / 60 ^th of the total volume Vt of catalyst of the reactor in operation: For example for a catalyst having 6 months of life with one regeneration per day, 1/180 ^th of the catalyst is replaced at each regeneration.

In particular in the case where the regenerations are very frequent, more than once a day for example, it is also, according to the invention, possible to carry out the partial loading / unloading of the catalyst not after each regeneration, but less frequently: it is possible to thus operate the partial loading / unloading every 2 or 3 regenerations for example, in thus adopting a lower loading / unloading frequency than the regeneration frequency.

The loading system preferably comprises a module for storing fresh catalyst, a module for feeding fresh catalyst to the reactor, and a dosing module taking the desired volume V1 of fresh catalyst from the storage module to the supply module. .

More particularly, according to an exemplary embodiment, the loading system may comprise, from upstream to downstream: - the catalyst storage module comprising a fresh catalyst storage tank, in particular of the hopper type, - the supply module with fresh catalyst from the reactor comprising a feed tank with a capacity smaller than the storage tank and fluidly connected to the catalyst inlet of the reactor, - and a metering module taking the desired volume V1 of fresh catalyst from the storage module to the feed module and comprising an intermediate loading tank, the capacity of which corresponds to the volume V1 of catalyst to be loaded, which is a fraction of the total volume Vt of the catalyst of the reactor in operation.

Throughout this text, the terms “upstream” and “downstream” relating to the catalyst are understood in relation to its general direction of flow in the reactor, from its introduction (feed) into one or more inlets in the reactor, up to when it is withdrawn from one or more outlets of the reactor.

Conventionally, the reactor is for example oriented substantially along a vertical axis, with one (s) catalyst inlet (s) in the upper part and one (s) catalyst outlet (s) in the lower part, the general direction of flow in question being then a downward vertical flow, under the effect of gravity. Any other orientation of the reactor and arrangements of the inputs / outputs are also possible.

The partial unloading system may include a module for withdrawing spent catalyst from the reactor, a module for storing spent catalyst, and a metering module taking the volume V'1 of used catalyst desired from the withdrawing module to the storage module. .

More particularly, according to an exemplary embodiment, the unloading system can comprise, from upstream to downstream, a module for withdrawing spent catalyst from the reactor. comprising a withdrawal tank fluidly connected to the catalyst outlet of the reactor, a spent catalyst storage module comprising a used catalyst storage tank, in particular of the hopper type, and a metering module taking the volume V'1 of spent catalyst desired from the withdrawal module to the storage module and comprising an intermediate unloading tank whose capacity corresponds to the volume V'1 of catalyst to be discharged, which is a fraction V'1 of the total volume Vt of the catalyst of the reactor in operation.

Advantageously, it is therefore possible to design the partial loading system and the partial unloading system fairly symmetrically, with for each three zones / parts: storage / dosing / supply or reactor withdrawal.

According to a variant of the invention, the partial loading system and / or the partial unloading system may / may be equipped with mechanical means facilitating the flow of the fresh / used catalyst to / from the reactor, in particular vibrators. . It may indeed prove useful to provide such means, since the catalyst intended to be in a fixed bed in reactors is generally not designed specifically to circulate.

The subject of the invention is also any set of at least two reactors as defined above, with at least part of the partial loading and / or unloading system which is shared for said assembly, in particular in the form of storage tanks. of common fresh and / or spent catalyst. It is thus possible to limit the number of additional equipment items induced by the invention.

A subject of the invention is also any set of pair (s) of reactors as defined above, where the two reactors of the / of each pair are associated to operate alternately, one of the reactors being in operating conditions. when the other reactor is either under regeneration conditions or under conditions of partial loading / unloading of catalyst. We thus always have one in two reactors that produce, which is a real gain in productivity compared to previous solutions where the ratio was rather 1 out of 3. The partial loading / unloading being fast, they only extend very much. reasonable reactor non-production time under regeneration conditions.

It should also be noted that the invention can be applied to reactors treating a feed either in liquid form, or in gaseous form, or in the form of a liquid / gas mixture, and preferably in gaseous form. The subject of the invention is also a fluid catalytic cracking installation (also called FCC), which integrates in its overhead effluent fractionation section a conversion unit, in particular of ethylene, comprising at least one reactor or set of reactors such as as defined above. Details on this fractionation, and on the conversion of ethylene so as to increase the production of propylene can for example be found in EP-3,428,249.

The subject of the invention is also a process for the catalytic treatment of hydrocarbons, using a reactor, in particular with radial circulation, comprising a fixed catalyst bed and with periodic regeneration of the catalyst in situ, such that said reactor is placed in fluid connection. , on the one hand, upstream, with a system for partially loading fresh catalyst, and, on the other hand, downstream, with a system for partially unloading spent catalyst, and such that only part of the catalyst spent from the reactor with fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst with said partial loading / unloading systems. Preferably, the partial loading and / or the partial unloading of catalyst relate to a volume of catalyst V1 corresponding to between 1/10 ^th and 1/200 ^th of the total volume Vt of catalyst of the reactor in operation, and the loading system (31 , 32) comprises a module for storing fresh catalyst, a module for supplying fresh catalyst to the reactor, and a dosing module: the desired volume V1 of fresh catalyst is taken from the storage module to the supply module by this dosing module.

The subject of the invention is also any process for the catalytic treatment of a hydrocarbon feed using a reactor or a set of reactors as defined above.

The subject of the invention is in particular such a process for treating a hydrocarbon feed obtained from a catalytic cracking unit.

The subject of the invention is also such a process for treating a predominantly low-carbon hydrocarbon feedstock, in particular C1 to C4, in gaseous and / or liquid phase, in particular with a view to enriching it with C2 to C4 olefins, and in aromatic.

A subject of the invention is also any process for the catalytic treatment of hydrocarbons, using a reactor, in particular with radial circulation, comprising a fixed catalyst bed and with periodic regeneration of the catalyst in situ, such that only a part is replaced. spent catalyst from the reactor with fresh catalyst after at least one, preferably every, in situ regeneration of the catalyst.

According to one embodiment, part of the effluent at the outlet of / from each reactor is recycled at the inlet of the reactor. Recycling can be useful for a number of reasons. On the one hand, it generally allows for a better load conversion rate. On the other hand, when the reaction (s) targeted in the reactor are of the exothermic type, recycling part of the effluent, optionally after cooling, makes it possible to keep the temperature within the reactor under control, and thus avoid runaway of reactions.

Optionally, it is therefore possible to treat the outlet effluent to be recycled before reintroduction into the reactor, in particular by a treatment of compression, cooling, or other type ...

A subject of the invention is also the process for implementing a set of pair (s) of associated reactors as defined above, or the process for the catalytic treatment of hydrocarbons as defined above, where the process uses one or more pairs of reactors, where, alternately one of the reactors of the / of each pair is in operation while the other reactor is in regeneration then in partial loading / unloading of catalyst.

A subject of the invention is also the process as defined above, and which performs the periodic regeneration of the catalyst of / each reactor by burning the coke deposited on the catalyst in the presence of oxygen. It is indeed the deposits of coke, residues of side reactions, which deactivate / passivate, for the most part, the catalysts gradually.

Advantageously, the periodic regeneration of the catalyst of / each reactor is carried out between a preliminary step of inerting (of the gas phase) in the reactor, and a subsequent step of inerting again (of the gas phase located in the reactor. ). It is in fact preferable: the preliminary stage makes it possible to empty the reactor of gaseous hydrocarbons which may be present before introduction of gas containing oxygen (air for example), and the subsequent stage makes it possible to remove the oxygen. contained in the reactor before switching it to production mode.

Preferably, only part of the catalyst is replaced (in particular by carrying out the partial loading / unloading of the catalyst with the partial loading / unloading systems described above), from the reactor after the regeneration of the reactor. catalyst and before, during or after the subsequent inerting step which follows said regeneration.

As indicated above, the replacement can be carried out at each regeneration, but it is also possible to carry it out on only some of the regenerations, at a (lower) difference frequency, therefore, in particular in the case where regenerations must be carried out at a high frequency. , less than 24 hours.

Preferably, the loading and partial unloading of catalyst is controlled by a system of valves fitted to the partial loading / unloading systems, said valves allowing or not the flow by gravity in desired quantities of the fresh catalyst in the reactor and of the spent catalyst. out of the reactor, preferably concomitantly. The loading / unloading systems thus comprise different tanks connected to each other and to the reactor by pipes equipped for example with valves, the opening or closing of which block or unblock the circulation catalyst throughout said systems and to / from the reactor. These are preferably automated controlled valves.

It is also possible to proceed without valves, by using gas injection means: an inert gas is injected into the partial loading / unloading systems, making it possible to stop the flow of catalyst at different locations of the device (s). systems, stopping the injection then allowing the catalyst to circulate at the desired location. And of course, it is also possible to use both valves and gas injection means.

Radial circulation reactors with a fixed catalyst bed lend themselves particularly well to the implementation of the invention, in particular by allowing the introduction and partial withdrawal of the catalyst by simply using gravity: the catalyst which has suffered the most. regenerations will necessarily be in the lowest part of this type of reactor oriented generally vertically, and it is therefore easily, by gravity, by withdrawing the spent catalyst from the bottom part during the partial unloading of catalyst, that we will unloading the most regenerated catalyst, therefore the oldest, the most worn, which is exactly what is wanted in the invention.

An example of the design of a fixed-bed radial reactor on which the invention can be applied is described in patent FR-3 033 264. List of Figures

Figure 1 shows an arrangement of three reactors operating in "swing" mode according to the prior art.

Figure 2 shows an arrangement of two reactors operating according to a new "swing" mode according to the invention.

Figure 3 shows an example of a partial load system of a reactor of the invention according to the arrangement of Figure 2.

Figure 4 shows an example of a partial unloading system of a reactor of the invention according to the arrangement of Figure 2.

Figure 5 shows in vertical section an example of a fixed bed radial reactor to which the invention according to Figures 2 to 4 can be applied.

Description of embodiments

All of the figures are very schematic, and the different elements that compose them are not necessarily to scale.

The embodiment of the invention of Figures 2 to 5 is given for illustrative purposes only and is not limiting of the invention.

FIG. 1 is a representation of a group of three reactors 1, 2, 3 operating conventionally in "swing" mode: reactor 1 is in operation, that is to say it is in production mode, while that the reactor 2 is in regeneration and that the reactor 3 is waiting or changing catalyst.

The three reactors 1, 2, 3 are identical and of the type with radial distribution and with a fixed catalyst bed (a design example of which is detailed later using FIG. 5): they are oriented vertically, with one or more feed inlets in the upper part, and one / more feed outlets in the lower part, the catalyst being retained in a catalytic bed between two concentric grids and the feed, in this case a gas, passing through said catalytic bed: there is a flow of the feed, up and down the reactor. Likewise, the introduction of fresh catalyst takes place through one or more inlets in the upper part, and the spent catalyst is withdrawn through one or more outlets in the lower part. Other reactor configurations are of course possible, and other types of feed, for example in liquid form, also possible.

To give an example of application, these reactors are intended to convert ethylene obtained from FCC as detailed in the aforementioned patent EP-3 428 249. The catalyst used for this conversion is generally zeolite, in particular of the alumino-silicate type. like ZMS-5.

The cycle time of this type of catalyst is short, and so is its lifespan. It therefore effectively takes three reactors, and a change of catalyst on one of the reactors 3 while the other reactors are one 1 in operation and the other 2 in regeneration. Reactor 1, in operation, is connected to the reaction circuit (not shown) by valves 4 and 5 which are open. The other valves leading to the reaction circuit, namely valves 6 and 7 for reactor 2 and valves 8 and 9 for reactor 3, are closed. The reactor 2, in regeneration, is connected by the valves 10 and 11, which are open, to the regeneration circuit, the other valves leading to the regeneration circuit (not shown), namely the valves 12 and 13 for the reactor 1 and valves 14 and 15 for reactor 3 are closed.

Other valves are connected to a purge system (not shown): valves 16 and 17 for reactor 1, valves 18 and 19 for reactor 2, valves 20 and 21 for reactor 3. This purge system allows the injection of an inert gas to make the transition between the production method where hydrocarbons are present, and regeneration, where oxygen is present to burn the coke deposited on the catalyst. Reactor 3 is either on standby or open for the change of catalyst. Only one reactor, reactor 1 in the figure, is in operation, and it takes 3 reactors to produce over a whole year.

In operation, each of the reactors 1, 2, 3 will therefore be alternately in production mode, in regeneration mode or in standby mode, like a circular permutation.

Depending on the desired conversion, depending on the nature of the catalyst, the selectivity of the conversion can change a little up to very significantly between the start and the end of the catalyst's life: in the case of a significant change in selectivity, it is necessary to add more reactors to smooth production, with for example two or three reactors in operation, and as many in regeneration, and still others pending.

Figure 2 shows an arrangement of two reactors in accordance with the present invention. Compared to figure 1, two notable changes, which will also be described with the aid of Figures 3 and 4: On the one hand, in terms of process, we only need two reactors, 1, 2, instead of three, reactor 1 being in production mode when l 'other, the reactor 2, is in regeneration mode + loading and partial unloading of catalyst, with switching from one mode to another alternately of each of the reactors. On the other hand, in terms of reactor design, each of the reactors 1, 2 is equipped with a partial loading system 31 of fresh catalyst and a partial unloading system 32 of spent catalyst.

Figure 3 details an example of a partial loading system 31 of fresh catalyst, with its storage module, its dosing module and its supply module, connected to each other by a system of pipes equipped with appropriate valves to control the flow of fresh catalyst in the desired quantity and at the desired time from the storage module in the reactor: the storage module here comprises a hopper 321, which is used to store the fresh catalyst for the number of weeks or months of operation decided in advance. This hopper can be inerted with nitrogen to keep the catalyst in good condition. Its pressure is preferably slightly higher than atmospheric pressure. This hopper is loaded once or more times a year, opening and loading it like loading a reactor, which can be done while the reactor is in operating mode. Below this hopper 321, the catalyst is retained by the valve 322, normally closed. This valve can be composed, for example, of a guillotine valve retaining the catalyst, and, below, a gas-tight valve closing on the empty catalyst pipe. This arrangement is an example, other types of embodiments are possible using, for example, an injection of inert gas blocking the flow of catalyst.

Below is the airlock 323, the capacity of which must correspond to the amount of catalyst that we want to replace at each regeneration, this is the dosing module mentioned above. Below this airlock is the valve 324 which can be composed like valve 322 of a knife gate valve retaining the catalyst and below a gas-tight valve closing on the empty catalyst piping. Here again, this embodiment is an example, and an injection of inert gas can replace the valve.

Below this valve is the fresh catalyst feed module, namely the upper hopper 325, the function of which is to distribute the catalyst to the catalyst inlet (s) provided in the upper part of the reactor. As detailed below with the aid of FIG. 5, it may be a question of a plurality of inlet conduits (12 “legs”) in a crown which will supply the reactor uniformly. A connection from an inerting gas such as nitrogen is provided to the airlock balloon 323. To bring catalyst from the storage hopper 321 to the airlock balloon 323, it is provided that the valve 324 is closed, the valve 327 closed, and the valve 326 open, so as to have the same pressure in the airlock balloon as in the hopper. At this time, the valve 322 is open and the catalyst will circulate by gravity from the upper hopper 321 to the airlock tank 323. When the level in the airlock tank 323 will reach the high level (the detection can be performed for example using gamma rays, in a known manner), the valve 322 is then closed (first the guillotine valve part closing on the catalyst, then the gas-tight valve part closing on the empty pipe to make gas tightness). The valve 326 is then closed, then the valve 327 opened in order to pressurize the airlock balloon 323 with the aid of inerting gas such as nitrogen.

The valve 327 is then closed, and the valve 328 opened to balance the pressures between the airlock 323 and the upper hopper 325. The catalyst can then flow when the valve 324 opens, which can be done when the valve 324 opens. a zone was liberated in the reactor after the spent catalyst had flowed out.

When the catalyst is in very regular bead-like grains (distribution of diameters restricted around a median value), the flow will be very easy. When in grains of less regular size / shape or even extrudates, flow can be aided by vibrators installed on the catalyst flow lines.

FIG. 4 details an example of a system for partially discharging spent catalyst. The partial unloading (like the partial loading) is advantageously done just after regeneration, at the time of purges of the gas phase of the reactor by inerting, to have an inert gas everywhere, and that the unloaded catalyst is regenerated, no longer containing any hydrocarbons. , no coke, so it can be handled safely and without problem.

The radial type reactor 2 is equipped with 12 catalyst withdrawal legs, connected to the lower hopper 329 (see description in FIG. 5 below). The unloading system comprises a withdrawal module in the form of a hopper 329, connected by a connection pipe to the dosing module in the form of an airlock tank 331. The connection pipe is equipped with a valve 330 (of preferably, comprising in fact two valves, one guillotine closing on the catalyst, and another sealed valve below closing on the empty pipe, other embodiments without a valve being possible). The airlock balloon 331 is connected by a lower pipe provided with the valve 332 to the spent catalyst storage means in the form of a lower storage hopper 333 making it possible to store a large quantity of spent catalyst. The lower airlock tank 331 has exactly the same capacity as the upper airlock tank 323, so that when the valves 330 and 324 are opened simultaneously, the valves 322 and 332 being closed, while the valves 335 and 328 will be open for balance the pressures, the fresh catalyst contained in the airlock 323 will flow into the reactor, while the spent catalyst contained in the reactor will flow lower in the reactor and the catalyst at the bottom of the reactor will s' flow into the airlock tank 331. When the high level is signaled in the airlock tank 331, the valve 330 will close (the guillotine valve on solid first, then the gas-tight valve on gas below then), then valve 324 will close, as will valves 328 and 335. The reactor is then ready for operation: the fraction of (spent) catalyst having undergone the maximum number of regenerations has been eliminated and replaced by an equal quantity of fresh catalyst.

The catalyst contained in the airlock 331 can then be transferred to the spent catalyst storage hopper 333: the valve 336 is open to balance the pressures, then the valve 332 is open. For this operation, as well as for the loading of the upper airlock tank, all the time is available when the reactor is in operation, then in regeneration. The catalyst contained in hopper 333 will cool slowly, and it can be discharged when the high alarm level is reached in this hopper: to be discharged, the cooled catalyst can be discharged into a dumpster (as shown below hopper 333) or drums or other containers.

What is remarkable about the invention is that the time necessary for the transfer of the spent catalyst out of the reactor and of the fresh catalyst into the reactor is very short compared to the regeneration and purge time: it is therefore not at all penalizing, since practically not "visible". On the other hand, the control of the installation gains greatly: in operating comfort, in the number of equipment and fast-acting, high-temperature valves. The footprint is reduced with the reduction in the number of reactors required for a given production, which also naturally reduces the cost of the unit (length of pipes, electrical wiring, concrete plinths, etc. )

FIG. 5 represents an example of a reactor 1, 2,3 with radial distribution and with a fixed bed to which the invention can be applied more particularly. This is a radial reactor, which is known to those skilled in the art, and used in processes with catalyst circulation, or sometimes to have low pressure drops in the reactor.

The fresh catalyst enters through conduits 53 distributed in a ring at the top of the reactor, called “catalyst legs”. We can have for example twelve connections regularly distributed around the conduit 51, so as to load the catalyst more or less homogeneously into the reactor. In the reactor, the catalyst is contained between the central manifold 55, and the outer grid 56. The spent catalyst exits through the conduits 54, which are also distributed in a ring around the outlet conduit 52. There may for example be twelve conduits. 54.

The charge enters through the central duct 51 at the head of the reactor, a deflector 57 forces the charge to pass between the shell 58 and the outer grid 56, then through the catalyst to enter inside the central manifold 55, the product exits through line 52 at the bottom of the reactor.

It is easy to install vibrators on all the catalyst "legs" in order to facilitate the partial replacement of the envisaged catalyst, at the inlet and at the outlet of the reactor.

The invention will be detailed using a non-limiting example:

Examples

Comparative example 1 (according to figure 1 and figure 5)

A catalyst consisting of ZSM-5 zeolite and silica is used. This catalyst converts ethylene into propylene, butene and aromatics, as well as some co-products. The ethylene conversion section is inserted into an FCC catalytic cracking unit, it allows from the ethylene intended to be burned with the fuel gas to increase the yields of recoverable products: propylene and aromatics in particular. The reaction is carried out at a temperature of 550 ° C, in a radial reactor of the type of that of FIG. 5 or of the aforementioned patent, and at an ethylene partial pressure of 1.5 bar. The catalyst is deactivated in a few hours, it is therefore necessary to operate with several reactors 1, 2, 3, one being in regeneration 2 when the other 1 is in operation, and a third reactor 3 remaining in reserve to replace the catalyst in operation, as illustrated in Figure 1.

The feed arriving at the ethylene conversion section has a flow rate of 21,520 kg / h, with the following composition (in mole%):

Nitrogen: 17.7

Hydrogen: 14.2

Methane: 27.3

Ethane: 13.8

Ethylene: 13.6 Propane 0.3

Propylene 3.3

Butane 0.4

Butenes 0.1

Petrol 4.2

Water 0.5

CO 1, 0

C0 ₂ 3.6

As the conversion is partial, part of the effluent is recycled to reactor 1, which also makes it possible to reduce the reaction exothermicity, and to avoid having several reactors in series. The recycling considered is 19,920 kg / h. The pressure at the inlet of reactor 1 is 9 bar absolute, which allows for an olefin partial pressure of 1.5 bar. The temperature of the reactor is 550 ° C. The operation is carried out with a single reactor, and a temperature increase of 40 ° C. in the reactor.

The composition at the reactor outlet is as follows (in mol%):

Nitrogen: 18.6

Hydrogen: 14.9

Methane: 28.7

Ethane: 14.5

Ethylene: 2.6

Propane: 0.7

Propylene: 10.1

Butane: 0.7

Butenes: 0.4

Gasoline: 3.5

Water: 0.5

CO: 1.0

C0 ₂ : 3.8

Regeneration is carried out using the dedicated reactor 2, at the same pressure and at the same temperature as the operation. The quantity of catalyst contained in each reactor is 3.2 tonnes, or approximately 4.5 m ³ .

The catalyst is operated for 12 hours in reactor 1, and the purging and regeneration operations in reactor 2 take a little less than 12 hours. Every 12 hours, the reactors are exchanged: the one that has the regenerated catalyst is put into operation, and the one whose catalyst begins to deactivate is purged, then regenerated. During the regenerations, the catalyst loses some of its activity and it is necessary to increase the temperature. When it is no longer possible to increase the temperature because the maximum allowable temperature for the reactor is reached, reactor 1 must be removed from operation (after regeneration), and reactor 3 filled in operation must be introduced. of fresh catalyst. The spent catalyst is drained from the reactor, fresh catalyst is introduced, which will allow the second reactor to be replaced, the second reactor will be emptied, and fresh catalyst will be introduced to be ready for the next change. If the lifespan of the catalyst is 2 months, it will be necessary to do all these operations every 2 months, with the temperature changes, and the downstream operation problems during the catalyst change.

Example 2 according to the invention (according to Figures 2 - 4 and 5)

We keep the same load, the same radial reactor. But we only produce with two reactors 1, 2, in accordance with Figures 2 to 4.

At the end of each regeneration, automatically replacing 1/60 ^th of the catalyst, 75 liters, so that the operating temperature does not change.

Balloons 323 and 331 of Figures 3 and 4 are sized to each hold 75 liters. Thanks to a vibrator (not shown), once the valves 330 and 335 open and the valves 332, 334 and 336 closed (FIG. 4), the reactor partially empties into the flask 331; 75 liters will then be missing at the head of the reactor, which will be filled with the contents of the flask 323 (FIG. 3). Valves 330 and 335 are then closed.

With another vibrator (also not shown), once the valves 322, 326 and 327 are closed, and the valves 324 and 328 open, the catalyst contained in the flask 323 is transferred into the reactor 2. The valves 324 and 328 are then closed, and the valves 326 and 322 open to transfer into the flask 323 the 75 liters required for the next regeneration. Valve 327 can be opened to pressurize flask 323 under nitrogen to the same pressure as the reactor.

Below the reactor (Figure 4), the valves 332 and 336 are open to transfer the 75 liters of spent catalyst into the storage hopper 333. The flask 331 remains free for the next regeneration. The valves 332 and 336 are then closed, and the valve 334 open to pressurize the balloon 331 to the same pressure as the reactor.

With the same load as in the previous comparative example, a gas is obtained at the outlet of identical composition: with the invention, the conversion rate and the selectivity are maintained. The same result is therefore obtained with 1/3 less reactor. With this gradual and almost continuous catalyst change, the age of the catalyst is homogenized in the production reactor during the production cycle, operating conditions are maintained, and in particular the temperature in the production reactor without having to adapt them according to the aging of the catalyst. And portion-wise catalyst change is easy to implement, and can be largely automated with the controllable valve sets.

Claims

1. Reactor (1, 2) for the catalytic treatment of hydrocarbons, in particular with radial circulation, comprising a fixed catalyst bed and with periodic regeneration of the catalyst in situ, characterized in that said reactor is in fluid connection, on the one hand, in upstream, with a system (31, 32) for partial loading of fresh catalyst, and, on the other hand, downstream, with a system (33,34) for partial unloading of spent catalyst, said systems replacing only part of the catalyst spent from the reactor by fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst, in that the partial loading and / or partial unloading of catalyst relate to a volume of catalyst V1 corresponding to between 1/10 ^th and 1/200 ^th of the total volume of the reactor catalyst Vt in operation, and in that the loading system (31, 32) comprises a fresh catalyst storage module, a power module in fresh catalyst from the reactor, and a dosing module taking the desired volume V1 of fresh catalyst from the storage module to the supply module.

2. Reactor (1, 2) according to the preceding claim, characterized in that the / each partial loading of fresh catalyst and the / each partial unloading of spent catalyst relates to identical catalyst volumes.

3. Reactor (1, 2) according to one of the preceding claims, characterized in that the partial loading of fresh catalyst and the partial unloading of spent catalyst are concomitant.

4. Reactor (1, 2) according to one of the preceding claims, characterized in that the partial loading and / or partial unloading of catalyst relate to a volume of catalyst V1 corresponding to between 1/20 ^th and 1/100 ^th or between 1 / 30th and ^I 1 / ^60th of the total volume Vt of the catalyst in reactor operation.

5. Reactor (1, 2) according to one of the preceding claims, characterized in that the loading system (31, 32) comprises, from upstream to downstream, the catalyst storage module comprising a storage tank (321 ) of fresh / regenerated catalyst, in particular of the hopper type, the module for supplying the reactor with fresh catalyst comprising a supply tank (325) of smaller capacity than the storage tank and fluidly connected to the catalyst inlet of the reactor, and a dosing module taking the desired volume V1 of fresh catalyst from the storage module to the supply module and comprising an intermediate loading tank (323) of which the capacity corresponds to the volume V1 of catalyst to be loaded, which is a fraction of the total volume Vt of the catalyst of the reactor in operation.

6. Reactor (1, 2) according to one of the preceding claims, characterized in that the system (33,34) for partial unloading comprises a module for withdrawing spent catalyst from the reactor, a module for storing spent catalyst, and a metering module taking the volume V'1 of used catalyst desired from the withdrawal module to the storage module.

7. Reactor (1, 2) according to the preceding claim, characterized in that the unloading system (33,34) comprises, from upstream to downstream, a module for withdrawing spent catalyst from the reactor comprising a withdrawal tank (329 ) fluidly connected to the catalyst outlet of the reactor, a spent catalyst storage module comprising a spent catalyst storage tank (333), in particular of the hopper type, and a metering module taking the desired volume V'1 of spent catalyst from the withdrawal module to the storage module and comprising an intermediate unloading tank (331) whose capacity corresponds to the volume V'1 of catalyst to be discharged, which is a fraction V'1 of the total volume Vt of the catalyst of the reactor in surgery.

8. Reactor (1, 2) according to one of the preceding claims, characterized in that the partial loading system (31, 32) and / or the partial unloading system (33,34) is / are equipped (s) mechanical means facilitating the flow of the fresh / spent catalyst to / from the reactor, in particular vibrators.

9. Set of at least two reactors (1, 2) according to one of the preceding claims, characterized in that at least part of the loading system (31, 32) and / or partial unloading (33,34 ) is pooled for said assembly, in particular in the form of common fresh and / or used catalyst storage tanks.

10. Set of pair (s) of reactors (1, 2) according to one of claims 1 to 9, characterized in that the two reactors of the / of each pair are associated to operate alternately, one of the reactors being in operating conditions when the other reactor is either under regeneration conditions or under conditions of partial loading / unloading of catalyst.

1 1. Process for the catalytic treatment of hydrocarbons, using a reactor (1, 2), in particular with radial circulation, comprising a fixed catalyst bed and with periodic regeneration of the catalyst in situ, characterized in that said reactor is placed in fluid connection, on the one hand, upstream, with a system (31, 32) for partially loading fresh catalyst, and, on the other hand, downstream, with a system (33,34) for partially discharging spent catalyst, in that only part of the spent catalyst from the reactor is replaced by fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst with said partial loading / unloading systems, in that the partial loading and / or partial unloading of catalyst relate to a volume of catalyst V1 corresponding to between 1/10 ^th and ^1/200 ^th of the total volume Vt of catalyst of the reactor in operation, in that the loading system (31, 32) comprises a module for storing fresh catalyst, a module for feeding fresh catalyst to the reactor, and a dosing module, and in that the volume V1 of catalyst is taken off wanted charge from storage module v to the supply module by the dosing module.

12. Process for the catalytic treatment of hydrocarbons, using the reactor (1, 2) according to one of claims 1 to 10, characterized in that only part of the spent catalyst from the reactor is replaced by fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst.

13. The method of claim 1 1 or 12, characterized in that the periodic regeneration of the catalyst of the reactor (1, 2) is carried out between a preliminary stage of inerting in the reactor, and a subsequent stage of inerting in said. reactor, and in that part of the spent catalyst from the reactor is replaced by fresh catalyst after regeneration of the catalyst and before, during or after the subsequent inerting step following said regeneration.

14. Method according to one of claims 1 1 to 13, characterized in that the replacement of a portion of the spent catalyst from the reactor by fresh catalyst by gas injection means and / or by a system is controlled. valves equipping partial loading (31, 32) / partial unloading (33,34) systems, said valves allowing or not the flow by gravity in desired quantities of fresh catalyst in the reactor and spent catalyst out of the reactor, preferably concomitantly.

15. Reactor (1, 2) according to one of claims 1 1 to 14, characterized in that the / each partial loading of fresh catalyst and the / each partial unloading of spent catalyst relates to identical catalyst volumes, and are of concomitant preference.