EP1343857A1

EP1343857A1 - Method for hydrotreatment of a heavy hydrocarbon fraction with switchable reactors and reactors capable of being shorted out

Info

Publication number: EP1343857A1
Application number: EP00990056A
Authority: EP
Inventors: Pascal Tromeur; Stéphane Kressmann
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2000-12-11
Filing date: 2000-12-11
Publication date: 2003-09-17
Anticipated expiration: 2020-12-11
Also published as: WO2002048288A1; NO20032620L; KR100783448B1; CN1484684A; CN1322097C; AU2001226863A1; NO20032620D0; BR0017384A; JP4697571B2; NO332312B1; DE60029645D1; MXPA03005072A; EP1343857B1; BR0017384B1; CA2432022A1; JP2004519533A; DE60029645T2; KR20030059837A; US20040055934A1

Abstract

The invention concerns a method for hydrotreating a heavy hydrocarbon fraction in a first hydrodemetallation section, then in a second hydrodesulphurization section into which the effluent is made to pass from the first section. The hydrodemetallation section is preceded by at least a guard zone. Said hydrotreatment comprises the following steps: a) a step, wherein the guard zone is used; b) a step, during which the guard zone is shorted out and the catalyst it contains is regenerated and/or replaced; c) a step, during which the guard zone whereof the catalyst has been regenerated and/or replaced is re-connected; d) a step during which at least one of the reactors of the hydrodemetallation section and/or of the hydrodesulphurization section can be shorted out and the catalyst it contains regenerated and/or replaced.

Description

PROCESS FOR HYDROTREATING A HEAVY FRACTION OF HYDROCARBONS WITH PERMUTABLE REACTORS AND SHORT-CIRCUITABLE REACTORS

The present invention relates to the refining and conversion of heavy fractions of hydrocarbons containing inter alia sulfur and metallic impurities, such as distillates or atmospheric residues, vacuum residues, deasphalted oils, vacuum distillates, pitches, asphalts mixed with an aromatic distillate, carbon hydrogenates, heavy oils of all origins and in particular from tar sands or shales. It relates in particular to the treatment of liquid charges. It would not be departing from the scope of the present invention if the liquid charge also contains asphaltenes.

The fillers which can be treated according to the invention usually contain at least 0.5 ppm by weight of metals (nickel and / or vanadium), at least 0.5% by weight of sulfur.

The objective of the catalytic hydrotreatment of these feeds is both to refine, that is to say to significantly reduce their content of metals, sulfur and other impurities while improving the hydrogen to carbon ratio (H / C) and while transforming them more or less partially into lighter cuts, the different effluents thus obtained can serve as bases for the production of good quality fuel oil, diesel and petrol, or fillers for other units such as cracking residue or cracked residue from vacuum distillates.

The problem posed by the catalytic hydrotreatment of these feedstocks comes from the fact that these impurities are gradually deposited on the catalyst in the form of metals and coke, and tend to deactivate and quickly clog the catalytic system, which requires a shutdown. for its replacement. The hydrotreatment processes of this type of feed must therefore be designed so as to allow the longest possible operating cycle without stopping the unit, the objective being to reach at least one year of operating cycle.

Various treatments for this type of charge exist. These treatments have been carried out so far:

- either in processes, preferably with fixed beds or bubbling beds of catalyst (for example the HYVAHL-F process of the Institut Français du

Oil),

- or in processes comprising at least one reactor allowing the quasi-continuous replacement of the catalyst (such as for example the HYVAHL-M moving bed process of the French Petroleum Institute).

The process of the present invention is an improvement on the processes of the prior art, in particular processes in fixed beds or bubbling beds of catalyst. In fact, in such processes, the charge circulates through several reactors, preferably with a fixed bed or a bubbling bed arranged in series, the first reactor (s) being used to especially carry out hydrodetallization of the charge therein (so-called step HDM) as well as part of the hydrodesulfurization, the last reactor (s) being used to carry out deep refining of the feedstock, and in particular hydrodesulfurization (so-called HDS step). The effluents are withdrawn from the last HDS reactor.

In such processes, use is most often made of specific catalysts adapted to each step, under average operating conditions, that is to say pressures generally between approximately 5 MPa and approximately 25 MPa, preferably between approximately 10 MPa and around 20 MPa and temperatures generally between about 340 ° C and about 440 ° C.

For the HDM stage, the ideal catalyst must be capable of treating fillers which may be rich in asphaltenes, while having a high demetallizing power combined with a high metal retention capacity and great resistance to coking. The Applicant has developed such a catalyst on a particular macroporous support (with a "sea urchin" structure) which gives it precisely the qualities sought in this step (patents EP-B-113297 and EP-B-113284):

- Demetallization rate of at least 10% to 90% in the HDM stage;

- Metal retention capacity generally greater than 10% relative to the weight of the new catalyst, which makes it possible to obtain longer operating cycles;

- High resistance to coking even at temperatures above 390 ° C which contributes to the lengthening of the cycle times, often limited by the increase in pressure drop and loss of activity due to the production of coke, and which makes it possible to carry out the essential of the thermal conversion in this stage.

For the HDS stage, the ideal catalyst must have a strong hydrogenating power in order to achieve a deep refining of the products: desulphurization, further demetallization, lowering of the Conradson carbon and possibly of the asphaltenes content. The applicant has developed such a catalyst (patents EP-B-113297 and EP-B-113284) which is particularly well suited to the treatments of this type of filler. The disadvantage of this type of catalyst with high hydrogenating power is that it deactivates quickly in the presence of metals or coke. This is why by combining an appropriate HDM catalyst, capable of operating at relatively high temperature to carry out most of the conversion and demetallization, with an appropriate HDS catalyst which, being protected from metals and other impurities by the HDM catalyst, can be operated at relatively low temperature which goes in the direction of a deep hydrogenation and the limitation of coking. Finally, overall refining performance is obtained which is superior to that obtained with a single catalytic system or to that obtained with a similar HDM / HDS arrangement using an increasing temperature profile which leads to rapid coking of the HDS catalyst.

The advantage of fixed bed processes is that high refining performance is obtained thanks to the high catalytic efficiency of fixed beds. On the other hand, above a certain metal content of the feed (for example from 50 to 150 ppm), although using the best catalytic systems, it can be seen that the performance and above all the operating time of these processes become insufficient: the reactors (in particular the first HDM reactor) are rapidly loaded with metals and therefore deactivate; to compensate for this deactivation, the temperatures are increased, which promotes the formation of coke and the increase in pressure drops; moreover, it is known that the first catalytic bed is liable to clog up fairly quickly because of the asphaltenes and sediments contained in the charge or following an operational incident.

It therefore follows that the unit has to be shut down at least every 2 to 6 months to replace the first deactivated or clogged catalytic beds, this operation being able to last up to 3 weeks, thereby reducing the factor unit operative. The advantage of the bubbling bed processes is that high conversion performance is obtained thanks to the possibility of working at high temperature. The applicant has developed such a process well suited to the treatment of conventional and heavy loads (patent CA 2,171,894 - French patent application FR-98 / 00.530)

Although using the best catalytic systems, we realize that the operating time can be reduced during operational problems or / and when used unsuitable for the load. It therefore follows that the unit is brought to a stop in view of the presence of coke in the reactor. Attempts have been made to resolve these problems of operation and use of catalyst.

We have also sought to solve the drawbacks of arrangements in fixed beds in different ways.

We thus thought of installing one or more reactors in a moving bed at the head of the HDM stage (US Patents US-A-3910834 or G B-B-2124252). These movable beds can work co-current (HYCON process from SHELL for example) or counter-current (HYVAHL-M process from the applicant for example). In this way, the reactors are protected, for example reactors in fixed beds, by carrying out part of the demetallization and by filtering the particles contained in the feed which can lead to clogging. In addition, the quasi-continuous replacement of the catalyst in this or these moving bed reactors avoids stopping the unit every 2 to 6 months.

The drawback of these moving bed technologies is that ultimately their performance and efficiency are generally lower than that of fixed beds of the same size, that they cause attrition of the circulating catalyst which can lead to blockage of the fixed beds located downstream, and that especially under the operating conditions used the risks of coking and therefore of formation of catalyst agglomerates are far from being negligible on these heavy loads, in particular in the event of incidents. These agglomerates can prevent the circulation of the catalyst, either in the reactor or in the spent catalyst withdrawal lines, and finally cause the unit to stop for cleaning the reactor and the withdrawal lines. To maintain the excellent performance while maintaining an acceptable operating factor, we also thought of adding a guard reactor, preferably in a fixed bed (VVH space speed = 2 to 4), in front of the HDM reactors (US-A patents -4118310 and US-A-3968026). Most often this guard reactor can be short-circuited, in particular by using an isolation valve. This provides temporary protection of the main reactors against clogging. When the standby reactor is clogged, it is short-circuited, but then, the main reactor which follows it can in turn clog and lead to the shutdown of the unit. In addition, the small size of this guard reactor does not ensure strong demetallization of the feedstock and therefore poorly protects the main HDM reactors against the deposition of metals in the case of feedstocks rich in metals (for example more than 100 ppm ). It follows an accelerated deactivation of these reactors leading to too rapid shutdowns of the unit, therefore to always insufficient operating factors.

It has also been described, in patent FR-B1-2 681 871, a system making it possible to combine the high performance of the fixed bed with a high operating factor for the treatment of loads with high metal contents

(1 to 1500 ppm but most often from 100 to 1000 and preferably from

150 to 350 ppm) which consists of a hydrotreatment process in at least two stages of a heavy fraction of hydrocarbons containing sulfur impurities and metal impurities. In this process, in a first so-called hydrodetallization section, the charge of hydrocarbons and hydrogen is passed under hydrodetallization conditions over a hydrodemetallization catalyst, then in a second subsequent section, hydrodesulfurization conditions, the effluent from the first section on a hydrodesulfurization catalyst. In this process, the hydrodetallization section comprises one or more hydrodemetallization zones, preferably in fixed beds, preceded by at least two hydrodetallization guard zones, also preferably in fixed beds, arranged in series to be used in a cyclic manner consisting of the successive repetition of steps b) and c) defined below: a) a step, in which the guard zones are used together for a duration at most equal to the deactivation and / or clogging time of one of them, b) a step , during which the deactivated and / or clogged guard zone is short-circuited and the catalyst that it contains is regenerated and / or replaced by fresh catalyst, and c) a step, during which the guard zones are used all together , the guard zone whose catalyst was regenerated during the previous step being reconnected and said step being continued for a duration at most equal to the deactivation and / or clogging of one of the guard zones.

This process allows a cycle time in general of at least 11 months for the main HDM and HDS reactors with high refining and conversion performances while maintaining the stability of the products. The global desulfurization is of the order of 90% and the overall demetallization of the order of 95%.

The disadvantage of this technology is the difficulty of obtaining performance in overall desulfurization greater than approximately 90% and / or in overall demetallization greater than approximately 95%, as well as the difficulty of obtaining cycle times greater than 11 months a few or the level of performance. It has surprisingly been found that bypassing one or more reactors of the hydrodemetallization section and / or of the hydrodesulfurization section makes it possible to maintain the catalytic activity for each of the stages and / or to improve the cycle time. The present invention thus relates to the possibility of short-circuiting one or more reactors when the catalyst is deactivated and / or clogged with sediment or coke to be regenerated and / or replaced by fresh or regenerated catalyst. This invention relates to reactors in the hydrodemetallization section as well as those in the hydrodesulfurization section.

It follows that the reactors of the hydrodemetallization and / or hydrodesulfurization section are for example short-circuited every 6 months to replace the deactivated or clogged catalytic beds, this operation improves the operating factor of the unit.

The invention consists of a process for hydrotreating a heavy fraction of hydrocarbons in a first hydrodemetallization section, then in a second hydrodesulfurization section through which the effluent from the first section is passed. The hydrodetallization section is preceded by at least one guard zone. Said hydrotreatment process comprises the following stages: a) a stage, in which the guard zone is used, b) a stage, during which the guard zone is short-circuited and the catalyst which it contains is regenerated and / or replaced c) a step, during which the guard zone whose catalyst has been regenerated and / or replaced is reconnected, d) a step in which at least one of the reactors of the hydrodetallization section and / or of the hydrodesulfurization section can be short-circuited and the catalyst it contains regenerated and / or replaced.

It has also been described, by the applicant in particular in patent FR-2 784 687, a way of improving the performance of the fixed bed, recalled below. This concept can also be applied to the present invention. There are also some difficulties related to the high viscosity of the charge and of the total liquid effluent which causes significant pressure drops in the reactor and difficulties in the operation of the recycling compressor, hence often a slightly low pressure d hydrogen which is not in favor of good hydrodemetallization or good hydrodesulfurization. Furthermore, it can be seen that the diesel fraction obtained is often not directly usable since its sulfur content is higher than current specifications.

It is thus desirable and possible to improve the performance of the methods described in French patents FR-B1-2 681 871 and FR 2 784 687. In particular the method of the present invention makes it possible to very significantly reduce the viscosity of liquid effluents, hence a significant reduction in pressure losses in the reactors, better operation of the recycling compressor and obtaining a higher hydrogen pressure. It is thus possible to obtain a greater overall desulfurization and a diesel fraction having a much lower sulfur content, meeting current specifications and directly usable in the diesel (storage) tank of the refinery. Furthermore, the method according to the invention makes it possible to obtain a better functioning of the preheating ovens thanks to a better heat transfer and therefore a lower skin temperature of these ovens which goes in the direction of a lifetime. of these ovens more important and is therefore a favorable factor allowing to decrease the operating cost of the unit.

The process according to the invention which combines the high performance of the reactors preferably in a fixed bed or bubbling bed, with a high operating factor for the treatment of feedstocks with high metal contents (1 to 1500 ppm but most often from 100 to 1000 and preferably 150 to 350 ppm) can be defined in one of its variants as a hydrotreatment process in at least two sections, of a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities, in which in a first so-called hydrodetallization section, the hydrocarbon and hydrogen charge is passed under hydrodetallization conditions over a hydrodetallization catalyst, then in a second subsequent section, the effluent from the first section is passed, under hydrodesulfurization conditions, over a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones, preferably in fixed beds or bubbling beds, preceded by at least one, or possibly two hydrodetallization guard zones, also preferably in fixed beds or bubbling beds, arranged in series to be used cyclically consisting of the successive repetition of the steps b) and c) defined below, the hydrodemetallization and / or hydrod sections Desulfurization are composed of one or more reactors, preferably in a fixed bed or in a bubbling bed which can be short-circuited separately or not according to step d) defined below. The method according to the invention, in the case where it involves two guard zones is therefore a hydrotreatment method comprising: a) a step, in which the guard zones are used all together for a duration at most equal to the time deactivation and / or clogging of one of them, b) a step, during which the deactivated and / or clogged guard zone is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step, during which the guard zones are used together, the guard zone whose catalyst has been regenerated and / or replaced during the previous step being reconnected and said step being continued for a duration at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodemetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged in order to be regenerated and / or replaced by fresh or regenerated catalyst.

Another variant of the process according to the invention consists of a process for hydrotreating in at least two sections, a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which in a first section called hydrodemetallization, passing, under hydrodetallization conditions, the charge of hydrocarbons and hydrogen over a hydrodemetallization catalyst, then in a second subsequent section, the effluent from the first stage is passed under hydrodesulfurization conditions on a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least one hydrodemetallization guard zone, the hydrodemetallization and / or hydrodesulfurization sections being composed of '' one or more reactors which can be short-circuited separately or not according to step d) defined above after, said hydrotreatment process comprising: a) a step, in which the guard zone is used for a duration at most equal to the deactivation and / or clogging time of said zone, b) a step, during which the zone guard deactivated and / or clogged is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step, during which the guard zone whose catalyst has been regenerated and / or replaced during the previous step is reconnected, said step being continued for a duration at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodemetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged in order to be regenerated and / or replaced by fresh or regenerated catalyst.

According to a variant of the process according to the invention, the charge of said process is a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities, in general at least 0.5 ppm by weight of metals, for example a fraction obtained by distillation vacuum also called vacuum distillate (DSV).

Preferably, in the process according to the invention, an amount of average distillate generally representing from 0.5% to 80% by weight is introduced at the entry of the first guard zone in operation, at the same time as the charge relative to the weight of the hydrocarbon charge.

More preferably, the amount of middle distillate introduced represents approximately 1% to approximately 50% and very preferably approximately 5% to approximately 25% by weight relative to the hydrocarbon charge.

In a particular embodiment, the atmospheric distillate which is introduced with the hydrocarbon feedstock is a direct distillation gas oil. According to another embodiment, the product resulting from the hydrodesulfurization step is sent to an atmospheric distillation zone. from which an atmospheric distillate is recovered, at least part of which is recycled at the entrance to the first guard zone in operation and an atmospheric residue.

According to a particular variant, at least part of a diesel fraction from atmospheric distillation is recycled. In this case the diesel cut that we recycle is most often a cut whose initial boiling point is around 140 ° C ° C and the final boiling point around 400 ° C. Most often this cut is a 150 ° C-370 ° C, or 170-350 ° C cut. According to another possible variant of the process according to the invention, it is possible to recycle a gas oil coming from a unit operating according to the HYVAHL process, or else a fraction of light gas oil coming from a catalytic cracking unit, most often called by a person skilled in the art under the initials LCO (from the English term Light Cylcle Oil) with an initial boiling point generally between approximately 140 ° C and approximately 220 ° C and with a final boiling point generally between approximately 340 ° C and about 400 ° C. It is also possible to recycle a fraction of heavy diesel fuel from catalytic cracking and most often called by a person skilled in the art under the initials HCO (from the English term High Cycle Oil), with an initial boiling point generally between approximately 340 ° C and about 380 ° C and final boiling point generally between about 350 ° C and about 550 ° C

The amount of atmospheric distillate and / or of diesel that is recycled represents, by weight relative to the feed, approximately 1 to 50%, preferably 5 to 25% and more preferably approximately 10 to 20%.

According to another variant, at least part of the atmospheric residue from the atmospheric distillation zone is sent to a vacuum distillation zone from which a vacuum distillate is recovered, at least part of which is recycled at the inlet of the first guard zone in operation and a vacuum residue which can be sent to the fuel oil storage zone of the refinery.

According to another variant, at least part of the atmospheric residue and / or of the vacuum distillate is sent to a catalytic cracking unit, preferably a catalytic cracking unit in a fluidized bed, for example a unit such as that using the process developed by the applicant called R2R. From this catalytic cracking unit, an LCO fraction and an HCO fraction are recovered in particular, which can be at least partly either one or the other, or a mixture of the two add to the fresh charge which is sends in the hydrotreatment process according to the present invention. A diesel fraction, a petrol fraction and a gaseous fraction are also most often recovered. At least part of this diesel fraction can optionally be recycled at the entrance to the first guard zone in operation.

The catalytic cracking step can be carried out in a conventional manner known to those skilled in the art, under the appropriate residue cracking conditions, with a view to producing hydrocarbon products of lower molecular weight. Descriptions of operation and of catalysts which can be used in the context of cracking in a fluidized bed are described, for example, in patent documents US-A-4,695,370, EP-B-1,84517, US-A-4,959,334, EP-B-323,297, US -A-4965232, US-A-5120691, US-A-5344554, US-A-5449496, EP-A-485259, US-A-5286690, US-A-5324696 and EP-A-699224 whose descriptions are considered incorporated herein by the mere fact of this mention.

The catalytic cracking reactor in a fluidized bed can operate with rising current or with falling current. Although this is not a preferred embodiment, it is also conceivable to carry out catalytic cracking in a moving bed reactor. Particularly preferred catalytic cracking catalysts are those which contain at least one zeolite usually in admixture with a suitable matrix such as, for example, alumina, silica, silica-alumina.

The implementation of the method according to the invention comprises a particular variant in which during step c) the guard zones are used all together, the guard zone whose catalyst was regenerated during step b) being reconnected so that its connection is identical to that which it had before it was short-circuited during the step b).

The implementation of the method according to the invention comprises another variant, which constitutes a preferred embodiment of the present invention, comprising the following steps: a) a step, in which the guard zones are used all together for a period of time at most equal to the deactivation and / or clogging time of the guard zone furthest upstream from the overall direction of circulation of the treated charge, b) a step, during which the charge penetrates directly into the guard zone located immediately after that which was most upstream during the previous stage and during which the guard zone which was most upstream during the previous stage is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step, during which the guard zones are used together, the guard zone whose catalyst has been regulated neutralized and / or replaced during the previous step being reconnected so as to be downstream of all the guard zones and said step being continued for a duration at most equal to the deactivation and / or clogging time of the guard zone which is, during this stage, the most upstream with respect to the overall direction of circulation of the charge treated. d) a step in which at least one of the reactors of the hydrodemetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged in order to be regenerated and / or replaced by fresh or regenerated catalyst. In the preferred embodiment of the process, the guard zone furthest upstream in the overall direction of flow of the charge is progressively charged with metals, coke, sediments and other various impurities and is disconnected as soon as desired, but most often when the catalyst qu 'it contains is practically saturated with metals and various impurities.

In a preferred embodiment, a particular conditioning section is used which allows these guard zones to be switched on, that is to say without stopping the operation of the unit: firstly, a system which operates at moderate pressure (from 1 MPa to 5 MPa but preferably from 1.5 MPa to 2.5 MPa) allows the following operations to be carried out on the disconnected guard reactor: washing, stripping, cooling, before discharging the spent catalyst; then heating and sulfurization after loading the fresh or regenerated catalyst; then another system of pressurization / depressurization and of gate valves of appropriate technology effectively makes it possible to permute these guard zones without stopping the unit, that is to say without affecting the operating factor, since all the washing operations, stripping, unloading of spent catalyst, recharging of fresh or regenerated catalyst, heating, sulfurization are carried out on the reactor or disconnected guard zone.

The reactors of the hydrotreating unit most often operate with the following hourly space velocities (VVH):

VVH (h-1) VVH (h " ¹ ) wide range preferred

Total HDM section: 0.2 - 4.0 0.3 - 0.4

(including guard reactors)

Total HDS section: 0.2 - 4.0 0.25 - 0.4

Overall (HDM + HDS): 0.10 - 2.0 0.12 - 0.3 A preferred mode consists in operating the guard zones or reactors in service at a global VVH of approximately 0.1 to 4.0 h ^-1 and most often of approximately 0.2 to 1.0 h ^-1 , at Unlike other methods using smaller guard reactors, in particular that described in US Pat. No. 3,968,026, where smaller guard reactors are used. The VVH value of each guard reactor in operation is preferably around 0.5 to 8 hr ^{"" 1} and most often around 1 to 2 hr ^-1 . The overall VVH value of the guard reactors and that of each reactor are chosen so as to achieve the maximum hydrodemetallization (HDM) while controlling the reaction temperature (limitation of exothermicity).

In an advantageous embodiment the unit will include a conditioning section, not shown in the figures, provided with adequate circulation, heating, cooling and separation means operating independently of the reaction section, allowing by means of pipes and valves to carry out the operations for preparing the fresh or regenerated catalyst contained in the guard reactor and or the reactor short-circuited just before being connected, unit in operation, namely: preheating of the reactor during permutation or short-circuited , sulfurization of the catalyst it contains, setting to the required pressure and temperature conditions. When the permutation or short-circuiting operation of this reactor has been carried out by means of the set of appropriate valves, this same section will also make it possible to carry out the operations of conditioning the spent catalyst contained in the reactor just after disconnection of the reaction section , namely: washing and stripping of the spent catalyst under the required conditions, then cooling before proceeding with the unloading operations of this spent catalyst, then replacement with fresh or regenerated catalyst More preferably, these catalysts are those described in the patents of the applicant EP-B-98764 and the French patent filed under the national registration number 97/07149. They contain a support and from 0.1 to 30% by weight, counted as metal oxides, of at least one metal or metal compound of at least one of groups V, VI and VIII of the periodic table of the elements and in the form of a plurality of juxtaposed agglomerates each formed of a plurality of needle-like plates, the plates of each agglomerate being oriented generally radially with respect to each other and with respect to the center of the agglomeration.

The present patent application relates more particularly to the treatment of heavy oils or heavy petroleum fractions, with the aim of converting them into lighter fractions, more easily transportable or treatable by the usual refining processes. Coal hydrogenation oils can also be processed. In this case, the use of bubble bed reactors will be preferred.

More particularly, the invention solves the problem of transforming a non-transportable, viscous heavy oil, rich in metals, sulfur and containing more than 50% of constituents with normal boiling point above 520 ° C. into a stable hydrocarbon product. , easily transportable, of low content of metals and sulfur and having only a reduced content, for example less than 20% by weight, of constituents with normal boiling point greater than 520 ° C.

In accordance with a particular embodiment, before sending the charge to the guard reactors, it is first mixed with hydrogen and it is subjected to hydroviscoreduction conditions. According to another embodiment, the atmospheric residue or the vacuum residue can be subjected to deasphalting using a solvent, for example a hydrocarbon solvent or a mixture of solvents. The most frequently used hydrocarbon solvent is a paraffinic, olefinic or cyclanic hydrocarbon (or mixture of hydrocarbons) having 3 to 7 carbon atoms. This treatment is generally carried out under conditions making it possible to obtain a deasphalted product containing less than 0.05% by weight of asphaltenes precipitated by heptane according to the AFNOR NF T 60115 standard. This deasphalting can be carried out by following the procedure described in patent US-A-4715946 in the name of the applicant. The volumetric solvent / charge ratio will most often be approximately 3: 1 to approximately 4: 1 and the elementary physicochemical operations that make up the overall deasphalting operation (mixing-precipitation, decantation of the asphaltenic phase, washing-precipitation of the asphaltic phase) will most often be carried out separately. The deasphalted product is then usually at least partially recycled at the entrance to the first guard zone in operation.

Usually the asphaltic phase washing solvent is the same as that used for precipitation.

The mixture between the charge to be deasphalted and the deasphalting solvent is most often produced upstream of the exchanger which adjusts the temperature of the mixture to the value required to achieve good precipitation and good decantation.

The charge-solvent mixture preferably passes through the tubes of the exchanger and not on the shell side.

The residence time of the charge-solvent mixture in the precipitation mixing zone is generally from approximately 5 seconds (s) to approximately 5 minutes (min), preferably from approximately 20 s to approximately 2 min. The residence time of the mixture in the settling zone is usually from about 4 min to about 20 min.

The residence time of the mixture in the washing zone generally remains between approximately 4 min and approximately 20 min.

The upward speeds of the mixtures both in the settling zone and in the washing zone will most often be less than approximately 1 cm per second (cm / s), and preferably less than approximately 0.5 cm / s.

The temperature applied in the washing zone will most often be lower than that applied in the settling zone. The temperature difference between these two areas will usually be about 5 ° C to about 50 ° C.

The mixture from the washing zone will most often be recycled in the decanter and advantageously upstream of the exchanger located at the entrance to the decantation zone.

The solvent / asphaltene phase ratio recommended in the washing zone is approximately 0.5: 1 to approximately 8: 1 and preferably approximately 1: 1 to approximately 5: 1.

The deasphalting may include two stages, each stage including the three basic phases of precipitation, decantation and washing. In this specific case, the temperature recommended in each phase of the first stage is preferably on average about 10 ° C. to about 40 ° C. lower than the temperature of each corresponding phase of the second stage. The solvents that are used can also be of the phenol, glycol or C1 to C6 alcohols type. However, paraffinic and / or olefinic solvents having 3 to 6 carbon atoms will be very advantageously used.

In summary, one of the variants of the process according to the invention consists of a process for hydrotreating in at least two sections, of a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which in a first section called hydrodemetallization, the hydrocarbon and hydrogen charge is passed under hydrodetallization conditions over a hydrodemetallization catalyst, then the effluent from the hydrodemetallization is passed, under hydrodesulfurization conditions the first step on a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least two hydrodemetallization guard zones arranged in series to be used in a cyclic manner consisting of the successive repetition of steps b) and c) defined below, the hydrodemetallization sections and / o u of hydrodesulfurization being composed of one or more reactors which can be short-circuited separately or not according to step d) defined below, said hydrotreatment process comprising: a) a step, in which the guard zones are used together for a period at most equal to the deactivation and / or clogging time of one of them, b) a step, during which the deactivated and / or clogged guard zone is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a stage, during which the guard zones are used all together the guard zone whose catalyst has been regenerated and / or replaced during the previous step being reconnected and said step being continued for a period at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst,

Another variant of the process according to the invention consists of a process for hydrotreating in at least two sections, a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which in a first section called hydrodemetallization, passing, under hydrodetallization conditions, the charge of hydrocarbons and hydrogen over a hydrodemetallization catalyst, then in a second subsequent section, the effluent from the first stage is passed under hydrodesulfurization conditions on a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least one hydrodemetallization guard zone, the hydrodemetallization and / or hydrodesulfurization sections being composed of '' one or more reactors which can be short-circuited separately or not according to step d) defined above after, said hydrotreatment process comprising: a) a step, in which the guard zone is used for a duration at most equal to the deactivation and / or clogging time of said zone, b) a step, during which the zone guard deactivated and / or clogged is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step, during which the guard zone whose catalyst has been regenerated and / or replaced during the previous step is reconnected, said step being continued for a duration at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst.

Another variant of the process according to the invention consists of a process for hydrotreating in at least two sections, a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which in a first section called hydrodemetallization, passing, under hydrodetallization conditions, the charge of hydrocarbons and hydrogen over a hydrodemetallization catalyst, then in a second subsequent section, the effluent from the first stage is passed under hydrodesulfurization conditions on a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least two hydrodemetallization guard zones comprising one or more reactors, preferably in fixed beds or in bubbling beds , arranged in series to be used cyclically consisting of the successive repetition of the steps b) and c) defined below, the hydrodemetallization and / or hydrodesulfurization sections being composed of one or more reactors which can be short-circuited separately or not according to step d) defined below, said hydrotreatment process comprising:

a) a step, in which the guard zones are used together for a duration at most equal to the deactivation and / or clogging time of the guard zone most upstream relative to the overall direction of circulation of the treated charge , b) a stage, during which the charge enters directly into the guard zone located immediately after that which was most upstream during the previous stage and during which the guard zone which was most upstream during the preceding stage is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a stage during which the guard zones are used all together, the guard zone including the catalyst has been regenerated and / or replaced during the previous step b) being reconnected so as to be downstream of all of the guard zones, said step being continued for a duration at most equal to the deactivation time and / or clogging of the guard zone which is, during this stage, the most upstream with respect to the overall direction of circulation of the charge treated, d) a stage in which at least one of the reactors of the The hydrodemetallization section and / or the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst.

Preferably, in the process according to the invention, an amount of average distillate representing from 0.5% to 80% by weight is introduced at the entrance to the first guard zone in operation, at the same time as the charge. the weight of the hydrocarbon charge. More preferably, the atmospheric distillate which is introduced with the hydrocarbon feedstock is a direct distillation gas oil.

In the process according to the invention, the product resulting from the hydrodesulfurization step is preferably sent to an atmospheric distillation zone from which an atmospheric distillate is recovered, at least part of which is preferably recycled at the inlet. of the first guard zone in operation, and an atmospheric residue. More preferably, at the entrance of the first guard zone in operation, at least part of a diesel fraction from the atmospheric distillation which follows the hydrodesulfurization step is recycled. According to a preferred variant of the process according to the invention, the recycled diesel fraction is a fraction with an initial boiling point of approximately 140 ° C. and a final boiling point of approximately 400 ° C.

In these preferred variants, the quantity of atmospheric distillate and / or of diesel introduced at the entry of the first guard zone in operation, at the same time as the charge preferably represents by weight relative to the charge approximately 1 to 50 %.

It is also possible to send at least part of the atmospheric residue from the atmospheric distillation zone to a vacuum distillation zone from which a vacuum distillate is recovered, at least part of which is recycled at the inlet. of the first guard zone in operation, and a vacuum residue. In this case, a variant consists in preferably sending at least part of the atmospheric residue and / or the distillate under vacuum in a catalytic cracking unit from which an LCO fraction and an HCO fraction are recovered and sent to the less in part either one or the other, or a mixture of the two fractions at the entrance to the first guard zone in operation.

According to one of the preferred modes of the method according to the invention, during step c) the guard zones are used all together, the guard zone whose catalyst was regenerated during step b) being reconnected so as to that its connection is identical to the one it had before it was short-circuited during step b). According to another preferred mode of the method according to the invention, the conditioning zone or zones is associated with a conditioning section which allows the short-circuiting or the permutation of said zone or zones of guard on operation, without stopping the operation of the unit, said section being adjusted so as to condition the catalyst contained in the guard zone which is not in operation, at a pressure of between 1 MPa and 5 MPa.

According to another preferred mode of the process according to the invention, in order to treat a feedstock consisting of a heavy oil or a heavy oil fraction containing asphaltenes, the feedstock is first subjected to hydroviscoreduction conditions , mixed with hydrogen, before sending the charge to the guard zone (s).

According to another preferred mode of the process according to the invention, the atmospheric residue obtained at the end of the optional atmospheric distillation step is subjected to deasphalting using a solvent or a mixture of solvent and the deasphalted product is at least partly recycled at the entrance to the first guard zone in operation.

According to another preferred mode of the process according to the invention, the vacuum residue obtained at the end of the optional vacuum distillation step is subjected to deasphalting using a solvent or a mixture of solvent and the deasphalted product is at least partly recycled at the entrance to the first guard zone in operation.

In one of the preferred variants of the process according to the invention, all the reactors are in a fixed bed. According to another preferred variant, at least one reactor of the guard zones and / or the hydrodematallation and / or hydrodesulfurization sections is a bubbling bed reactor. According to another preferred variant, the reactors in the guard zones are in a fixed bed, and all the reactors in the hydrodesulfurization zone are in a bubbling bed. According to yet another preferred variant, all the reactors in the guard zones are in a fixed bed, and all the reactors in the hydrodemetallization zone are in a bubbling bed, and possibly very preferably all the reactors in the hydrodesulfurization zone are also in a bubbling bed. It is also possible to operate the process according to the invention with only bubbling bed reactors in the guard zones and in the hydrodemetallization and hydrodesulfurization sections.

FIG. 1 briefly explains the invention by way of illustration.

The load arrives in the guard guard zones, designated 1A and 1B by the line 1 and leaves these zones via the line 13, via the lines 23 and / or 24. The load leaving the guard zone (s) arrives by the line 13 in the section of HDM which is represented here by a reaction section 2 consisting of one or more reactor (s), each of the reactors being provided with its own short circuit. The effluent from section 2 is withdrawn through line 14, then sent to a hydrodesulfurization section 3, which may include one or more reactors optionally in series, and optionally provided with their own short circuit. The effluent from section 3 is withdrawn through line 15

In the illustration of FIG. 1, a medium distillate is introduced via line 55 which mixes with the hydrocarbon charge in line 1.

In the case shown in FIG. 1, the guard zone comprises 2 reactors, the method, in its preferred embodiment, will comprise a series of cycles each comprising four successive periods: - a first period during which the load passes successively zone 1A then zone 1 B and in which the fraction diesel from atmospheric distillation which is recycled is introduced with the feed into zone 1A. During the first period [step a) of the process] the charge is introduced via line 1 and line 21, which has a valve 31 open, to the guard reactor 1A. During this period, the valves 32, 33 and 35 are closed. The effluent from zone 1A is sent to the guard reactor 1 B via line 23, line 26 which has a valve 34 open, and line 22. The effluent from zone 1 B is sent to section 2 of HDM through line 24 which has an open valve 36 and line 13 which has an open valve 37.

- a second period during which the charge crosses only zone 1 B and in which the diesel fraction from atmospheric distillation which is recycled is introduced with the charge into zone 1 B. During the second period [ step b) of the process] the valves 31, 33, 34 and 35 are closed and the charge is introduced by line 1 and line 22, which includes a valve 32 open, in zone 1 B. During this period the effluent from zone 1 B is sent to section 2 of HDM via line 24, which comprises an open valve 36, and line 13 which comprises an open valve 37.

a third period during which the charge successively crosses zone 1 B then zone 1A and in which the diesel fraction resulting from atmospheric distillation which is recycled is introduced with the charge into zone 1 B. During the third period [step c) of the process] the valves 31, 34 and 36 are closed and the valves 32, 33 and 35 are open. The charge is introduced via line 1 and line 22 to zone 1 B. The effluent from zone 1 B is sent via line 24, line 27 and line 21 into the guard reactor 1A. The effluent from zone 1A is sent to section 2 of HDM via line 23 and line 13, which has a valve 37 open. - A fourth period during which the charge only crosses the guard zone 1A and in which the diesel fraction from the atmospheric distillation which is recycled is introduced with the charge in the zone 1A. The number of cycles performed for the guard reactors is a function of the duration of the operating cycle of the entire unit and the average frequency of permutation of zones 1A and 1 B. During the fourth period the valves 32, 33, 34 and 36 are closed and the valves 31, and 35 are open. The charge is introduced via line 1 and line 21 to zone 1A. During this period the effluent from zone 1A is sent to section 2 of HDM via line 23 and line 13 which includes a valve 37 open.

In the case shown in FIG. 1, the hydrodemetallization section (HDM) can comprise one or more reactors, each or more of these reactors can be temporarily isolated for periodic renewal of the catalyst (s) [step d) of the process]. The method will comprise, in its preferred embodiment, a series of cycles each comprising three successive periods:

- a first period during which the load successively crosses the guard zones 1A, 1B, and section 2 of HDM, then finally section 3 of HDS. During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into the guard zone 1A. During this period the valves

32, 33, 35, 38 and 41 are closed. The charge is introduced via line 1 and line 21 to zone 1A. The effluent from zone 1 A is sent to the guard zone 1 B via line 23, line 26 which has a valve 34 open and line 22. The effluent from zone 1 B is sent to section 2 of HDM via line 24, which includes an open valve 36, and line 13 which includes an open valve 37. The effluent from section 2 is sent to section 3 of HDS via line 14 which has two open valves 42 and 39. The effluent from section 3 is then sent to a fractionation unit not represented by line 15 which has a valve 40 open.

- a second period during which the load successively crosses guard zones 1 A and 1 B, then section 3 of HDS. During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into zone 1 B. During this operation, the valves 32, 33, 35, 37, 41 and 42 are closed. The charge is introduced via line 1 and line 21 to zone 1A. The effluent from zone 1A is sent to the guard zone 1 B via line 23, line 26 which has a valve 34 open, and line 22. The effluent from zone 1 B is sent to section 3 HDS via line 24, which has an open valve 36, and line 25 which has two open valves 38 and 39. The effluent from section 3 is then sent to a fractionation unit not shown, via line 15 , which has a valve 40 open. During this period, the HDM catalyst is renewed, then said catalyst is conditioned according to the method described in this invention. This conditioning is particularly necessary if the catalyst is in oxide form.

- a third period during which the load successively crosses guard zones 1A and 1B, and section 2 of HDM, then finally section 3 of HDS. During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into the guard zone 1 B. This situation is identical to the first period and makes it possible to put the reactor containing the new catalyst in a identical position, inside the fluid circuit, compared to that described in the first period. In the case shown in FIG. 1, the hydrodesulfurization section 3 can comprise one or more reactors, each or more of these reactors can be temporarily isolated for periodic catalyst renewal [step d) of the process]. The method will comprise, in its preferred embodiment, a series of cycles each comprising three successive periods:

- a first period during which the load successively crosses guard zones 1A and 1B and section 2 of HDM, then section 3 of HDS. During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into the guard zone 1A. During this period the valves 32, 33, 35, 38 and 41 are closed. The charge is introduced via line 1 and line 21 into the guard zone 1A. The effluent from the guard zone 1A is sent to the guard zone 1 B via the line 23, the line 26 which has a valve 34 open, and the line 22. The effluent from the guard zone 1 B is sent to section 2 of HDM via line 24, which has an open valve 36, and line 13 which has an open valve 37. The effluent from section 2 is sent to section 3 via line 14 which has two open valves 42 and 39. The effluent from reactor 3 is then sent to a fractionation unit not represented by line 15 which includes an open valve 40.

- a second period during which the load successively crosses the guard zones 1A and 1B then section 2 of HDM.

During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into zone 1 B. During this operation, the valves 32, 33, 35, 38, 39 and 40 are closed. The charge is introduced into zone 1A via line 1 and line 21. The effluent from zone 1A is sent to zone 1B via line 23, line 26 which has a valve 34 open, and the line 22. The effluent from zone 1 B is sent to section 2 of HDM via line 24, which comprises an open valve 36, and line 13 which comprises an open valve 37. The effluent from section 2 is then sent to a fractionation unit not represented by line 14, which comprises an open valve 42, and line 16, which comprises an open valve 41. During this period, the catalyst or the catalysts of section 3 are renewed, then the catalyst (s) are conditioned according to the method described in this invention, this conditioning is particularly necessary when the catalyst is in oxide form.

a third period during which the load successively crosses guard zones 1A and 1B, section 2 of HDM, and finally section 3 of HDS. During this period, the diesel fraction from atmospheric distillation which is recycled is introduced with the feed into zone 1 B. This situation is identical to that described in period 1 and makes it possible to return the reactor (s) containing the new catalyst (s) catalyst (s) in the same position, inside the fluid circuit, as that described in the first period.

Claims

1. Process for hydrotreating in at least two sections, a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which, in a first so-called hydrodetallization section, is passed under hydrodetallization conditions, the load of hydrocarbons and hydrogen on a hydrodemetallization catalyst, then in a second subsequent section is passed, under hydrodesulfurization conditions, the effluent of the first step over a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least two hydrodemetallization guard zones arranged in series to be used in a cyclic manner consisting of the successive repetition of steps b) and c) defined below , the hydrodemetallization and / or hydrodesulfurization sections being composed of one or more reactors which may be short-circuited separately or not according to step d) defined below, said hydrotreatment process comprising: a) a step, in which the guard zones are used all together for a duration at most equal to the time of deactivation and / or clogging of one of them, b) a step, during which the deactivated and / or clogged guard zone is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a stage, during which the guard zones are used together, the guard zone whose catalyst has been regenerated and / or replaced during the preceding stage being reconnected and said stage being continued for a duration at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodetallization section and / or of the section hydrodesulfurization can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst.

2. Hydrotreatment process in at least two sections of a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which, in a first so-called hydrodetallization section, is passed under hydrodetallization conditions, the load of hydrocarbons and hydrogen on a hydrodemetallization catalyst, then in a second subsequent section is passed, under hydrodesulfurization conditions, the effluent of the first step over a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least one guard zone, the hydrodemetallization and / or hydrodesulfurization sections being composed of one or more reactors which can be short-circuited separately or not according to step d) defined below, said hydrotreatment process comprising: a) a step, in which the z guard one is used for a duration at most equal to the deactivation and / or clogging time of said zone, b) a step, during which the deactivated and / or clogged guard zone is short-circuited and the catalyst that it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step, during which the guard zone whose catalyst was regenerated and / or replaced during the previous step is reconnected, said step being continued for a duration at most equal to the deactivation and / or clogging time of one of the guard zones, d) a step in which at least one of the reactors of the hydrodetallization section and / or of the section hydrodesulfurization can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst.

3. Hydrotreatment process in at least two sections of a heavy fraction of hydrocarbons containing sulfur impurities and metallic impurities in which, in a first so-called hydrodemetallization section, is passed under hydrodetallization conditions, the load of hydrocarbons and hydrogen on a hydrodemetallization catalyst, then in a second subsequent section is passed, under hydrodesulfurization conditions, the effluent of the first step over a hydrodesulfurization catalyst, and in which the hydrodemetallization section comprises one or more hydrodemetallization zones preceded by at least two hydrodemetallization guard zones comprising one or more reactors, preferably in fixed beds or in bubbling beds, arranged in series to be used cyclically consisting of the successive repetition of steps b) and c) defined below, the hydrodemetal sections lization and / or hydrodesulfurization being composed of one or more reactors which can be short-circuited separately or not according to step d) defined below, said hydrotreatment process comprising:

a) a step, in which the guard zones are used together for a duration at most equal to the deactivation and / or clogging time of the guard zone most upstream relative to the overall direction of circulation of the treated charge , b) a stage, during which the charge enters directly into the guard zone lying immediately after that which was most upstream during the previous stage and during which the guard zone which was most upstream during from the previous step is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh or regenerated catalyst, c) a step during which the guard zones are used all together, the guard zone whose catalyst has been regenerated and / or replaced during the preceding step b) being reconnected so as to be downstream of the assembly guard zones, said step being continued for a period at most equal to the deactivation and / or clogging time of the guard zone which is, during this stage, the most upstream relative to the overall direction of circulation of the feedstock treated, d) a step in which at least one of the reactors of the hydrodemetallization section and / or of the hydrodesulfurization section can be short-circuited during the cycle when the catalyst is deactivated and / or clogged to be regenerated and / or replaced by fresh or regenerated catalyst.

4. Method according to one of claims 1 to 3 wherein there is introduced, at the entrance of the first guard zone in operation, at the same time as the charge, an amount of average distillate representing from 0.5% to 80 % by weight relative to the weight of the hydrocarbon feedstock.

5. The method of claim 4 wherein the atmospheric distillate which is introduced with the hydrocarbon feed is a direct distillation diesel.

6. Method according to one of claims 1 to 5 wherein the product from the hydrodesulfurization step is sent to an atmospheric distillation zone from which an atmospheric distillate is recovered, at least part of which is recycled to the atmosphere. entry of the first guard zone in operation, and an atmospheric residue.

7. The method of claim 6 wherein at the entrance of the first guard zone in operation is recycled at least part of a diesel fraction from atmospheric distillation following the hydrodesulfurization step.

8. The method of claim 5 or 7 wherein the diesel fraction is a section of initial boiling point of about 140 ° C and final boiling point of about 400 ° C.

9. Method according to one of claims 4 to 8 wherein the amount of atmospheric distillate and / or diesel introduced at the entrance of the first guard zone in operation, at the same time as the charge represents by weight relative to at the expense of approximately 1 to 50%.

10. Method according to one of claims 6 or 7 wherein at least part of the atmospheric residue from the atmospheric distillation zone is sent to a vacuum distillation zone from which a vacuum distillate is recovered, at least of which a part is recycled at the entrance to the first guard zone in operation and a vacuum residue.

11. The method of claim 10 wherein at least a portion of the atmospheric residue and / or the vacuum distillate is sent to a catalytic cracking unit from which an LCO fraction and an HCO fraction are recovered which is sent to the less in part either one or the other, or a mixture of the two at the entrance to the first guard zone in operation.

12. Method according to one of claims 1 and 3 in which during step c) the guard zones are used all together, the guard zone whose catalyst was regenerated during step b) being reconnected with so that its connection is identical to the one it had before it was short-circuited during step b).

13. Method according to one of claims 1 to 12 wherein one associates with the zone or zones of guard a conditioning section which allows the short-circuit or the permutation in operation of said zone or of said zones of guard, without stopping the operation of the unit, said section being adjusted so as to condition the catalyst contained in the guard zone which is not in operation, at a pressure of between 1 MPa and 5 MPa.

14. Method according to one of claims 1 to 13 wherein, in order to treat a load consisting of a heavy oil or a heavy oil fraction containing asphaltenes, the load is first subjected to conditions hydroviscoreduction, mixed with hydrogen, before sending the load to the guard zone (s).

15. Method according to one of claims 7, 10 or 11 in which the atmospheric residue is subjected to deasphalting using a solvent or a mixture of solvent and the deasphalted product is at least partially recycled to the entrance to the first guard zone in operation.

16. Method according to one of claims 10 or 11 in which the vacuum residue is subjected to a deasphalting with the aid of a solvent or a mixture of solvent and the deasphalted product is at least partly recycled to l entry of the first guard zone in operation.

19. Method according to one of claims 1 to 16 wherein all the reactors are in a fixed bed.

18 Method according to one of claims 1 to 17 wherein at least one reactors of the guard zones and / or hydrodematallation and / or hydrodesulfurization sections is a bubbling bed reactor.

19. The method of claim 18 wherein all the reactors of the guard zones are in a fixed bed, and all the reactors of the hydrodesulfurization zone are in a bubbling bed.

20. The method of claim 18 or 19 wherein all the reactors of the guard zones are in a fixed bed, and all the reactors of the hydrodemetallization zone are in a bubbling bed.