FR3097779A1 - Hydrocarbon catalytic treatment reactor with semi-continuous catalyst replacement - Google Patents

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 with periodic regeneration of the catalyst in situ, such that said reactor is in fluid connection, on the one hand, 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 spent catalyst from the reactor with fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst. Figure 2 to publish

Description

Catalytic hydrocarbon treatment reactor with semi-continuous catalyst replacement

The invention relates to the catalytic treatment of hydrocarbons. Catalysts are in fact used very widely in refining and petrochemical installations, in processes operating a certain number of reactions in parallel and/or in a 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 the isomerization of paraffins and naphthenes. Mention may also be made of 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 Anglo-Saxon term Fluid Catalytic Cracking, or the metathesis reactions of olefins etc.

To carry out all these reactions, there are different families of catalysts. They tend to wear out, deactivate/passivate gradually, which explains why they must periodically be replaced with “fresh” catalyst, and/or regenerated 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, generally by burning the coke. The cycle time is the operating time between two regenerations. At each regeneration, because of the high regeneration temperatures, the catalyst sinters, i.e. it loses some active surface. Over the 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 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 the annual type.

However, in some cases the catalyst does not have a long enough cycle time for this. Other solutions must then be considered.

A first solution consists in using 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 FCC type catalytic cracking units. It is a high-performance solution, but high-tech and therefore quite complex/expensive to implement.

There are other less complex/expensive solutions to implement, including a second solution known by the Anglo-Saxon term "swing", in rocker mode therefore: it consists of using a unit comprising several reactors operating in parallel, some being in operation mode while others are in catalyst regeneration mode, or else in standby or catalyst loading mode, with switching from one mode to another by control which may be automatic, in particular at the using suitable pilot operated valves. As it is moreover necessary to change the catalyst after a certain number of regenerations, concretely, for a reactor in production, it is therefore possible to have two reactors (the one in regeneration and the one awaiting catalyst) which do not produce, which does not is not excellent in terms of productivity. This second solution makes it possible to regenerate catalysts with a shorter lifetime/cycle, by avoiding, for the regeneration of the catalyst, the periodicity imposed by annual plant closures for example.

However, this second solution is not without drawbacks: in fact, in a given reactor in production mode, the catalyst gradually loses its activity over the regenerations, which forces the operating conditions to 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 again necessary to modify, very quickly this time, the operating conditions in the opposite direction, the temperature in particular. These periodic modifications of the operating conditions and a certain fluctuating character of results in terms of composition of effluent obtained, and yield, difficult to erase completely, are not without risk on the industrial level, more particularly when the outlet effluent of the reactor in production mode is then processed in a downstream distillation column. Indeed, a distillation column subjected to a sudden change in the composition of the feed can go out of adjustment, begin to oscillate, and it may take hours before finding products that meet specifications, which can lead to production losses. A first parade consists in providing several reactors in parallel production mode, 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 production fluctuations.

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

The object 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) while throughout a production campaign and/or in order to facilitate reactor control and/or in order to have a more productive installation.

The subject of the invention is first of all a reactor for the catalytic treatment of hydrocarbons, in particular with radial circulation, comprising a bed of fixed catalyst and with periodic regeneration of the catalyst in situ. Said reactor is in fluidic connection, on the one hand, upstream, with a system for partial loading of fresh catalyst, and, on the other hand, downstream, with a system for partial unloading of spent catalyst, said systems coming to replace a only part of the spent catalyst from the reactor with fresh catalyst after at least one, preferably each, 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 installation can operate the reactors in failover mode in pairs only, with one reactor in production for an unproductive/regenerating reactor (without the need for a third unproductive reactor, which was generally in the loading mode of catalyst or waiting for the loading in question). Indeed, while one of the reactors is in production, the other will be able to switch to regeneration mode and partial change of catalyst. 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 most “worn” portion of catalyst. This step is permitted by the systems according to the invention.

Taking the example of a catalyst which has a lifetime of 30 days, and in the case where the catalyst in question is regenerated once a day, this means that with the invention it will be possible, in the reactor in regeneration, just after its regeneration, change 1/ ^30th of the catalyst contained in the reactor, a volume therefore small, this change being able to be done quickly and easily thanks to the invention: everything then happens as if the replacement of the catalyst almost continuously, semi-continuously, so that the reactor will permanently contain 1/30 ^th of the catalyst having undergone one regeneration, 1/30 ^th of the catalyst having undergone two regenerations etc... Thus, the activity of the catalyst, will be globally, 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, to obtain products of constant quality and yield.

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

Preferably, the/each partial loading of fresh catalyst and the/each partial unloading of used catalyst concerns identical volumes of catalyst: a certain volume of "used" catalyst is therefore removed and replaced by an identical volume (with industrial tolerances close) of "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: it is thus possible to reduce as much as possible the time necessary for this double operation.

The partial loading and/or the partial unloading of catalyst may relate to a volume of catalyst V1 corresponding to between 1/ ^10th and 1/ ^200th , in particular between 1/ ^20th and 1/ ^100th or between 1/ ^30th and 1 /60 ^th of the total volume Vt of catalyst of the reactor in operation: For example, for a catalyst with a lifetime of 6 months 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 possible, according to the invention, to operate the partial loading/unloading of the catalyst not after each regeneration, but less frequently: one can thus operating the partial loading/unloading every 2 or 3 regenerations for example, thus adopting a loading/unloading frequency lower than the frequency of the regenerations.

The loading system preferably comprises a fresh catalyst storage module, a fresh catalyst supply module of the reactor, and a metering 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 fresh catalyst from the reactor comprising a feed tank of lower capacity 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 towards the feed module and comprising an intermediate loading tank whose 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.

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 into the reactor, until 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 catalyst inlet(s) in the upper part and catalyst outlet(s) in the lower part, the general direction of flow in question being then a vertical downward flow, under the effect of gravity. Any other orientation of the reactor and arrangements of the inlets/outlets are also possible.

The partial unloading system may comprise a spent catalyst withdrawal module from the reactor, a spent catalyst storage module, and a metering module withdrawing the desired spent catalyst volume V'1 from the withdrawal module to the storage module .

More particularly, according to an exemplary embodiment, the unloading system may comprise, from upstream to downstream, a spent catalyst withdrawal module from the reactor comprising a withdrawal tank fluidly connected to the catalyst outlet of the reactor, a storage module spent catalyst comprising a spent catalyst storage tank, in particular of the hopper type, and a metering module withdrawing the desired volume V'1 of spent catalyst from the withdrawal module to the storage module and comprising an intermediate unloading tank whose the 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, the partial loading system and the partial unloading system can therefore be designed fairly symmetrically, with three zones/parts for each: storage/metering/feeding 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 fresh/spent catalyst to/from the reactor, in particular vibrators . It may indeed prove useful to provide such means, insofar as the catalyst intended to be in a fixed bed in the reactors is generally not designed specifically for circulation.

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

The invention also relates to any set of pair(s) of reactors as defined above, where the two reactors of the/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 partial catalyst loading/unloading conditions. We thus always have one out of two reactors producing, which is a real gain in productivity compared to previous solutions where the ratio was more like 1 out of 3. The partial loading/unloading being fast, they only lengthen very much the non-production time of the reactor under regeneration conditions is reasonable.

It should also be noted that the invention can be applied to reactors processing a feedstock either in liquid form, or in gaseous form, or in the form of a liquid/gas mixture, and preferably in gaseous form.

The invention also relates to a fluid catalytic cracking installation (also called FCC), which incorporates in its overhead effluent fractionation section a conversion unit, in particular of ethylene, comprising at least one reactor or set of reactors such than 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 patent EP-3 428 249.

A subject of the invention is also any process for the catalytic treatment of hydrocarbon feedstock implementing a reactor or a set of reactors as defined above.

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

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

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

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

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

A subject of the invention is also the method for implementing a set of pair(s) of associated reactors as defined above, or the method for the catalytic treatment of hydrocarbons as defined above, where the method 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 carries out the periodic regeneration of the catalyst of the/each reactor by burning the coke deposited on the catalyst in the presence of oxygen. It is in fact the coke deposits, residues of parasitic reactions, which deactivate/passivate, for the most part, the catalysts gradually.

Advantageously, the periodic regeneration of the catalyst of the/of each reactor is carried out between a preliminary stage of inerting (of the gaseous phase) in the reactor, and a subsequent stage of inerting again (of the gaseous phase located in the reactor ). It is in fact preferable: the preliminary step allows the reactor to be emptied of any gaseous hydrocarbons present before the introduction of gas containing oxygen (air for example), and the subsequent step allows the oxygen to be removed 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), of the reactor after the regeneration of the catalyst and before, during or after the step posterior inerting 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 different (lower) frequency, therefore, in particular in the case where regenerations must be carried out at high frequency. , less than 24 hours.

Preferably, the loading and the partial unloading of catalyst are controlled by a system of valves fitted to the partial loading/unloading systems, said valves authorizing or not the flow by gravity in the desired quantities of the fresh catalyst in the reactor and of the spent catalyst. outside the reactor, preferably concomitantly. The loading/unloading systems thus comprise various 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 points of the device/ systems, stopping the injection then allowing the catalyst to circulate at the desired location. And it is of course 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 the partial withdrawal of the catalyst by simply exploiting gravity: the catalyst which has undergone the most of regenerations will necessarily be in the lowest part of this type of generally vertically oriented reactor, and it is therefore easily, by gravity, by withdrawing the spent catalyst from the lower part during the partial unloading of catalyst, that we will discharge the most regenerated catalyst, therefore the oldest, the most worn, which is exactly what is desired in the invention.

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

List of Figures

FIG. 1 represents an arrangement of three reactors operating in rocker (“swing”) mode according to the prior art.

FIG. 2 represents an arrangement of two reactors operating according to a new swing mode according to the invention.

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

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

FIG. 5 represents in vertical section an example of a fixed-bed radial reactor to which the invention according to FIGS. 2 to 4 can be applied.

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

The embodiment of the invention of Figures 2 to 5 is given purely by way of illustration and does not limit 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 reactor 2 is in regeneration and that reactor 3 is on standby or changing catalyst.

The three reactors 1,2,3 are identical and of the type with radial distribution and with a fixed catalyst bed (an example of a design of which is detailed later with the aid of FIG. 5): they are of vertical orientation, with one or more charge inlets in the upper part, and one or more charge outlets in the lower part, the catalyst being retained in a catalytic bed between two concentric grids and the charge, in this case a gas, passing through said catalytic bed: there is a flow of the load, from the top to the bottom of the reactor. Similarly, the introduction of fresh catalyst is done by one or more inlets in the upper part, and the withdrawal of spent catalyst is done by one or more outlets in the lower part.

Other reactor configurations are of course possible, and other types of charge, in liquid form for example, are also possible.

To give an example of application, these reactors are intended to convert ethylene 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 the ZMS-5.

The cycle time of this type of catalyst is short, and its life also. 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. Reactor 2, in regeneration, is connected by valves 10 and 11, which are open, to the regeneration circuit, the other valves leading to the regeneration circuit (not shown), namely valves 12 and 13 for 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 makes it possible to inject an inert gas to make the transition between the mode of production 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 catalyst change. 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 alternately be 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 from a little to very significantly between the start and the end of the life of the catalyst: 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 on standby.

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, only two reactors are needed, 1.2, instead of three, reactor 1 being in production mode when the other, reactor 2, is in regeneration mode + loading and partial unloading of catalyst, with passage from one mode to the other 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 metering 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 into 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 conditions. Its pressure is preferably slightly above atmospheric pressure. The loading of this hopper is done one or more times a year, by opening it and loading it as one loads 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, which is 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 pipe empty of the catalyst. This arrangement is an example, other types of realizations are possible by using for example an injection of inert gas coming to block the flow of catalyst.

Below is the airlock tank 323, the capacity of which must correspond to the quantity of catalyst that you want to replace at each regeneration, this is the dosing module mentioned above. Below this airlock tank is valve 324 which, like valve 322, can be made up of a knife gate valve retaining the catalyst and, below, a gas-tight valve closing on the empty catalyst pipe. Again, this embodiment is an example, and inert gas injection can replace valve control.

Below this valve is the fresh catalyst supply module, namely the upper hopper 325, whose function is to distribute the catalyst to the catalyst inlet(s) provided in the upper part of the reactor. As detailed later using Figure 5, it may be a plurality of inlet ducts (12 "legs") in a ring that will supply the reactor uniformly.

A connection from an inerting gas such as nitrogen is provided to the airlock tank 323. To bring catalyst from the storage hopper 321 to the airlock tank 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 bag-lock 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 reaches the high level (the detection being able to be carried out for example using gamma rays, in a known way), the valve 322 is then closed (first the part of the guillotine valve closing on the catalyst, then the part of the gas-tight valve closing on the empty pipe to make gas tightness). Valve 326 is then closed, then valve 327 opened to pressurize airlock balloon 323 using inerting gas such as nitrogen.

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

When the catalyst is in very regular ball-type grains (distribution of diameters tight around a median value), flow will occur very easily. When it is in grains of less regular size/shape or even extruded, the flow can be facilitated by vibrators installed on the catalyst flow lines.

Figure 4 details an example of a partial spent catalyst unloading system. Partial unloading (like partial loading) is advantageously done just after regeneration, when purging the gas phase of the reactor by inerting, to have an inert gas everywhere, and the discharged catalyst is regenerated, no longer containing any hydrocarbons , nor coke, so it can be handled without risk and without problems.

The reactor 2, of the radial type, is equipped with 12 catalyst withdrawal legs, connected to the lower hopper 329 (cf. 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 metering 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 piping, other embodiments without a valve being possible). The airlock tank 331 is connected by a lower pipe fitted with the valve 332 to the spent catalyst storage means in the form of a lower storage hopper 333 allowing a large quantity of spent catalyst to be stored.

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 will be closed, while the valves 335 and 328 will be open for balance the pressures, the fresh catalyst contained in the balloon-lock 323 will flow into the reactor, while the spent catalyst contained in the reactor will flow lower into the reactor and the catalyst at the bottom of the reactor will 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 gastight 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 bag-lock 331 can then be transferred into the spent catalyst storage hopper 333: the valve 336 is opened to balance the pressures, then the valve 332 is opened. For this operation, as well as for the loading of the upper airlock tank, we have all the time during which the reactor is in operation, then in regeneration. The catalyst contained in the hopper 333 will cool slowly, and it can be evacuated when the high alarm level is reached in this hopper: to be evacuated, the cooled catalyst can be unloaded into a skip (as shown under the hopper 333) or drums or other containers.

What is remarkable about the invention is that the time required to transfer the spent catalyst out of the reactor and 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 high-temperature fast-acting 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 bases, 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. It 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 the ducts 53 distributed in a ring at the top of the reactor, called “catalyst legs”. It is possible, for example, to have twelve connections regularly distributed around the conduit 51, so as to charge the catalyst in a more or less homogeneous manner in 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 shroud 58 and the outer grid 56, then through the catalyst to enter inside the central collector 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 catalyst envisaged, 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 transforms ethylene into propylene, butene and aromatics, as well as some co-products. The ethylene conversion section is inserted in 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 a partial pressure of ethylene 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 shown 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
Gasoline: 4.2
Water: 0.5
CO: 1.0
_CO2 : 3.6

As the conversion is partial, part of the effluent is recycled to reactor 1, which also makes it possible to reduce the exothermicity of the reaction, 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 makes it possible to have a partial pressure of olefins of 1.5 bar. The reactor temperature 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
_CO2 : 3.8

The regeneration is carried out thanks to 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, ie approximately 4.5 m ³ .

The catalyst is operated for 12 hours in reactor 1, and the purge and regeneration operations in reactor 2 take a little less than 12 hours. Every 12 hours, the reactors are exchanged: the one with the regenerated catalyst is put into operation, and the one whose catalyst is starting to deactivate is switched to purging, then to regeneration. Over 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 has been reached, reactor 1 must be removed from operation (after regeneration), and reactor 3 introduced into operation filled 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 life of the catalyst is 2 months, all these operations will have to be done every 2 months, with temperature changes, and operational problems downstream when changing the catalyst.

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 1.2 reactors, in accordance with Figures 2 to 4.

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

The balloons 323 and 331 of Figures 3 and 4 are sized to each contain 75 liters. Thanks to a vibrator (not shown), once the valves 330 and 335 are open and the valves 332, 334 and 336 are closed (FIG. 4), the reactor partially empties into the balloon 331; 75 liters will then be missing at the head of the reactor, which will be filled thanks to the contents of the balloon 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 balloon 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 tank 323 the 75 liters necessary for the next regeneration. Valve 327 can be opened to pressurize balloon 323 under nitrogen at the same pressure as the reactor.

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

With the same charge as in the previous comparative example, an outlet gas of identical composition is obtained: 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 change of catalyst, the age of the catalyst in the production reactor is homogenized during the production cycle, the operating conditions are maintained, and in particular the temperature in the production reactor without having to adapt them in depending on the aging of the catalyst. And the change of catalyst by portion is easy to implement, and can be largely automated with the sets of controllable valves.

Claims (14)

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 with fresh catalyst after at least one, preferably every, in situ regeneration of the catalyst. 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. 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. Reactor (1,2) according to one of the preceding claims, characterized in that 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 , in particular between ^1/20 and ^1/100 or about 1 / 30th ^me and ^1/60 of the total volume Vt of the catalyst in reactor operation. Reactor (1,2) according to one of the preceding claims, characterized in that the loading system (31,32) comprises a module for storing fresh catalyst, a module for supplying fresh catalyst to the reactor, and a module dosing unit taking the desired volume V1 of fresh catalyst from the storage module to the supply module. Reactor (1,2) according to the preceding claim, characterized in that the loading system (31,32) comprises, from upstream to downstream, the catalyst storage module comprising a storage tank (321) of fresh catalyst / regenerated, in particular of the hopper type, the module for supplying fresh catalyst to the reactor comprising a supply tank (325) of smaller capacity 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 supply module and comprising an intermediate loading tank (323) whose capacity corresponds to the volume V1 of catalyst to be charged, which is a fraction of the total volume Vt of the reactor catalyst in operation. Reactor (1,2) according to one of the preceding claims, characterized in that the partial unloading system (33,34) comprises a module for withdrawing spent catalyst from the reactor, a module for storing spent catalyst, and a module metering unit taking the volume V'1 of used catalyst desired from the withdrawal module to the storage module. 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) connected fluidically at 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 volume V'1 of used catalyst desired 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 unloaded, which is a fraction V'1 of the total volume Vt of the catalyst of the reactor in operation. 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 with means mechanical facilitating the flow of fresh / spent catalyst to / from the reactor, in particular vibrators. Assembly 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 storage tanks for common fresh and / or used catalyst. 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 operation. operating conditions when the other reactor is either under regeneration conditions or under conditions of partial loading / unloading of catalyst. 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 only part of the spent catalyst is replaced reactor with fresh catalyst after at least one, preferably each, in situ regeneration of the catalyst. Process according to the preceding claim, 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 this 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. Process according to one of Claims 12 or 13, characterized in that the replacement of part of the spent catalyst from the reactor by fresh catalyst is controlled by gas injection means and / or by a valve system fitted to the reactor. partial loading (31,32) / partial unloading (33,34) systems, said valves allowing or not allowing the flow by gravity in desired quantities of the fresh catalyst in the reactor and of the spent catalyst out of the reactor, preferably in a manner concomitant.