FR3054559A1 - HYDROPROCESSING PROCESS USING PERMUTABLE GUARD REACTORS WITH INVERSION OF FLOW SENSE AND PARALLEL REACTORS. - Google Patents

Abstract

The invention relates to a process for the catalytic hydrotreatment of a hydrocarbon heavy load, in the presence of hydrogen, comprising a step of prior hydrodemetallation using at least two reactors in fixed bed each comprising at least one catalytic bed, which are used cyclically according to the following steps: a) a step in which at least two reactors are used in series in downward flow until a pressure drop threshold Dpi of value between 20 and 70 is reached; % of the maximum allowable pressure drop DPmax, b) a step of inversion of the direction of flow and paralleling of the at least two reactors until reaching the maximum allowable pressure drop DPmax c) a step during which the first reactor is short-circuited and the catalyst it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is changed and only the reaction or reactants eur (s) not yet clogged (s) operate in downflow, d) a step during which said at least two reactors are used in series, the reactor whose catalyst has been regenerated in the previous step being reconnected and said step being continued until reaching a pressure drop threshold Dpi of value between 20 and 70% of the maximum allowable pressure drop DPmax, e) a reversal step of the direction of flow and of paralleling the two reactors until the maximum allowable pressure drop DPmax f) a step during which the second reactor is short-circuited and the catalyst contained therein is regenerated and / or replaced by catalyst cool, the direction of flow is changed and only the reactor (s) not yet clogged (s) operate in downward flow; said steps a), b), c), d), e), f) being repeatable cyclically in this order.

Description

Technical area

The invention relates to fixed bed processes, and more generally to hydrotreatment processes for heavy hydrocarbon feedstocks, in particular of residues or any hydrogenation of petroleum fractions which can cause clogging of the fixed bed.

Prior art

One of the problems posed by catalytic hydrotreatment in a fixed bed of heavy loads is clogging, especially in the upper part of the bed. The catalytic beds, more particularly the upper parts of the first catalytic bed in contact with the load, are liable to clog up fairly quickly because of the asphaltenes and sediments contained in the load, which is expressed initially by an increase in pressure drop (DP) and sooner or later requires a shutdown of the unit to replace the catalyst.

We are therefore forced to stop the unit to replace the first deactivated and / or clogged catalytic beds. 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.

A person skilled in the art has sought to overcome these drawbacks of arrangements in fixed beds in various ways, in particular by using guard beds arranged upstream of the main reactors. The main task of the guard beds is to protect the catalysts of the main downstream hydrotreatment reactors by carrying out part of the demetallation and by filtering the particles contained in the feed which can lead to clogging. Guardbeds contain at least hydrodemetallization catalyst, optionally supplemented by inert elements and / or prelites (grading in English) and are generally integrated in the HDM hydrodemetallization section in a hydrotreating process for heavy loads including generally a first hydrodemetallization section, then a second HDT hydrotreating section. Although guard beds are generally used to carry out a first hydrodemetallization and filtration, other hydrotreatment reactions (hydrodesulfurization HDS, hydrodenitrogenation HDN ...) will inevitably take place in these reactors thanks to the presence of hydrogen and d 'a catalyst.

The technology known as PRS (Permutable Reactors System) is described in patents FR2681871 and US5417846 of the Applicant. The patent FR2681871 describes a hydrotreatment process in at least two stages of a heavy fraction of hydrocarbons containing asphaltenes, sulfur impurities and metallic impurities in which during the first so-called hydrodemetallization stage is passed , under hydrodemetallization conditions, the charge of hydrocarbons and hydrogen on a hydrodemetallization catalyst, then during the second subsequent step, the effluent from the first stage is passed under hydrodesulfurization conditions on a hydrodesulfurization catalyst characterized in that the hydrodemetallization step comprises one or more hydrodemetallization zones in fixed beds preceded by at least two hydrodemetallization guard zones also in fixed beds, arranged in series to be used cyclically consisting of the successive repetition of steps b) and c) defined below and in that it comprises the following steps: 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 guard zone deactivated and / or clogged is short-circuited and the catalyst it contains is regenerated and / or replaced by fresh catalyst, and c) a step, during which the guard zones are used together, the guard zone whose catalyst has been regenerated during the previous step being reconnected and said step being continued for a duration at most equal to the deactivation time

This technology allows an extension of the lifetime of the catalysts present in the downstream reactors by permutation and change of catalyst without stopping the process completely. This principle has been improved by patents:

US2014001089, which describes a process for hydrotreating heavy loads of hydrocarbons with permutable reactors including at least one step of progressive permutation.

And US2014027351 which describes a process for hydrotreating heavy loads of hydrocarbons with permutable reactors including at least one step of short-circuiting a catalytic bed.

Patent FR2992971 describes a process for hydrotreating heavy loads in a catalytic fixed bed with reversing the direction of flow of fluids using at least one co-current fixed bed reactor descending from a gas phase and from a liquid phase in which during the operating cycle of said process, the direction of flow of the fluids is reversed to become ascending, the pressure drop threshold triggering the flow reversal is defined from a value DP1 between DP1 and DP1 + ( 0.5xDP2), DP1 being defined as the pressure drop at the start of the cycle and DP2 as the pressure drop at the end of the cycle equal to the maximum admissible pressure drop by the process equipment.

These systems remain controlled by an increase in the overall pressure drop of the bed. When the pressure drop increases too much, it is necessary to unload and reload the reactor. There is a real loss of catalytic activity because the discharged catalyst is not completely deactivated.

Object of the invention

The invention constitutes an improvement of existing technologies aimed at extending the cycle time of PRS-type permutable reactors, through optimal use of the available fluxes and better use of the catalyst present in the reactors.

To this end, a step of reversing the direction of flow and placing the reactors in parallel is inserted each time one of the two permutable reactors begins to clog, therefore when the pressure drop reaches a value- threshold Dpi defined by a person skilled in the art as a function of the maximum admissible pressure drop DPmax in the equipment.

Description of the invention

Summary of the invention

The invention relates to a process for the catalytic hydrotreatment of a heavy hydrocarbon feedstock, in the presence of hydrogen, comprising a preliminary hydrodemetallization stage by means of at least two reactors which are permutable in a fixed bed, each comprising at least one catalytic bed, which are used cyclically according to the following stages:

a) a step in which at least two reactors are used in series in downward flow until reaching a pressure drop threshold Dpi of value between 20 and 70% of the maximum admissible pressure drop DPmax,

b) a step of reversing the direction of flow and placing said at least two reactors in parallel until the maximum admissible pressure drop DPmax is reached

c) a stage during which the first reactor brought into contact with the feed in stage a) is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) not yet clogged (s) operate in downflow,

d) a step during which said at least two reactors are used in series, the reactor whose catalyst was regenerated during the previous step being reconnected and said step being continued until a loss threshold is reached Dpi load value between 20 and 70% of the maximum admissible pressure drop DPmax,

e) a step of reversing the direction of flow and placing the two reactors in parallel, until the maximum admissible pressure drop DPmax is reached

f) a stage during which the second reactor brought into contact with the feed in stage a) is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) not yet clogged (s) operate in downflow; said steps a), b), c), d), e), f) can be repeated cyclically in this order.

In one embodiment, at least one of the reactors comprises n catalytic beds and the effluent from said reactor is removed in steps b) and / or e) by a lateral withdrawal between a catalytic bed i and a catalytic bed i + 1, n being an integer greater than or equal to 2, i being an integer ranging from 1 to n.

Preferably, said catalytic bed i + 1 designates the first catalytic bed clogged in the direction of flow.

Said at least two permutable reactors can all comprise at least two catalytic beds.

Preferably, the pressure drop threshold Dpi has a value between 30 and 60% of the maximum admissible pressure drop DPmax.

Very preferably, the pressure drop threshold Dpi has a value between 35 and 50% of the maximum admissible pressure drop DPmax.

The heavy hydrocarbon feedstock advantageously has an initial boiling temperature of at least 340 ° C and a final boiling temperature of at least 440 ° C.

The feedstock can be chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, headless crude oils, deasphalt resins, asphalt or deasphalting pitches, residues from conversion processes, extracts aromatics from base production chains for lubricants, oil sands or their derivatives, oil shales or their derivatives, mother rock oils or their derivatives, taken alone or as a mixture.

Preferably, the charge is chosen from atmospheric residues or vacuum residues, or mixtures of these residues.

The hydrotreatment process according to the invention is advantageously carried out at a temperature between 320 ° C and 430 ° C, under a partial hydrogen pressure between 3 MPa and 30 MPa, at a space speed (WH) between 0.05 and 5 charge volume per catalyst volume and per hour, and with a gaseous hydrogen to liquid hydrocarbon charge ratio of between 200 and 5000 normal cubic meters per cubic meter.

The preliminary hydrodemetallization stage can be carried out in the presence of a hydrodemetallization catalyst comprising at least one metal from group VIII, and / or at least one metal from group VIB, on a support used chosen from the group formed with alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals, preferably at a space speed WH of each reactor which can be switched in operation between 0.5 and 4 volumes of charge per volume of catalyst and per hour, very preferably at a space speed WH of each reactor which can be switched in operation between 1 and 2 volume of charge per volume of catalyst and per hour.

In general, the maximum admissible pressure drop DPmax is between 0.3 and 1 MPa, preferably between 0.5 and 0.8 MPa.

List of Figures

Figure 1: Switchable PRS reactor device according to the prior art (FR2681871)

Figure 2: Reactor device according to the invention

Figure 3: Reactor device according to an embodiment with short-circuiting of a catalytic bed according to the invention.

Figure 4: Evolution of the pressure drop in each PRS swappable reactor according to the sequence of FR2681871

Figure 5: Evolution of the pressure drop in each PRS permeable reactor according to the sequence according to the invention

Detailed description of the invention

The present invention provides an improvement of existing technologies aimed at extending the cycle time of PRS reactors.

The proposed improvement is aimed at new units as well as existing units with a few modifications (lines, valves, reactor internals, down flow and up flow distributor, etc.). The present invention consists in reversing the direction of flow during the operating cycle of the PRS switchable reactor system. When a reactor begins to clog, therefore when the pressure drop begins to increase and reaches a threshold value Dpi defined by a person skilled in the art as a function of the maximum admissible pressure drop in the reactors (DPmax), the load is injected simultaneously into the two permutable reactors placed in parallel, so as to plug the upper layer first, then the lower layer of the catalytic bed, which results in a more homogeneous clogging, and gives an increase in the pressure drop more slow, thus leading to an increase in cycle time.

More particularly, the present invention relates to a process for hydrotreating a heavy fraction of hydrocarbons generally containing asphaltenes, sediments, sulfur, nitrogen and metallic impurities, in which it is passed beforehand, under hydrotreatment conditions , the charge of hydrocarbons and hydrogen on a hydrotreatment catalyst, in at least two permutable reactors in a fixed bed, each containing at least one catalytic bed,

It has now surprisingly been discovered that it is possible to increase the service life of the swappable reactors before the replacement of the catalyst contained in the swappable reactors becomes necessary. The present invention thus improves the performance of the swappable reactors as described by the applicant in patent FR2681871, by incorporating, after the stages during which the charge successively passes through all the reactors, additional stages, in which the direction of flow is reversed and the two reactors put in parallel. Thus, during these additional steps, the charge is simultaneously introduced on two reactors. This reversal of the direction of flow makes it possible to delay the rise in the pressure drop of the first reactor brought into contact with the load and thus lengthens its service life.

The introduction of part of the charge onto the second reactor while another part of the charge continues to pass through the first reactor brought into contact with the charge also makes it possible to relieve the first reactor and also to make optimum use all the catalyst present in the reactor.

The main advantage of this sequencing is not only better use of the catalyst present in each reactor, but also a better distribution of the liquid flows, the two reactors not necessarily being clogged in the same proportions (due to the prior operation in series , the quantity of sealant loaded in each of the reactors is significantly different). In addition, the problems of possible fluidization linked to the change of direction are limited, because the flow of fluids is divided by two (which justifies all the more to pass in parallel flow), which limits the need for recourse to additional grids-type equipment to contain the expansion of the bed due to fluidization.

The loading / unloading of each of these reactors is done on increase in the pressure drop DP only, when one of the reactors is completely clogged, the active phase of the downstream catalyst being used in the best way. The reactors downstream of the PRS swappable reactors will have an increased service life and better use of the catalytic charge.

Features of the invention

The swappable reactors used as guard zones), in particular the first guard zone brought into contact with the feed, gradually become charged with metals, coke, sediments and other various impurities. When the catalyst or the catalysts which they contain or the space (s) inter-grain of catalyst is / are practically saturated (S) in metals and various impurities, the reactors must be disconnected to carry out the replacement or the regeneration of catalyst (s). Preferably, the catalysts are replaced. This moment is called deactivation and / or clogging time. Although the deactivation and / or clogging time varies depending on the charge, the operating conditions and the catalyst (s) used, it is generally expressed by a drop in catalytic performance (an increase in the concentration of metals and / or other impurities in the effluent), an increase in the temperature necessary for maintaining constant hydrotreatment or, in the specific case of clogging, by a significant increase in the pressure drop. The pressure drop DP, expressing a degree of clogging, is measured continuously throughout the cycle on each of the reactors and can be defined by an increase in pressure resulting from the partially blocked passage through the reactor.

In order to define a deactivation and / or clogging time, the person skilled in the art previously defines a maximum tolerable value of the pressure drop DP max (referred to below as the maximum admissible pressure drop) depending of the charge to be treated, the operating conditions and catalysts chosen, and from which it is necessary to proceed to the disconnection of the permutable reactor

The deactivation and / or clogging time is thus defined as the time when the limit value of the pressure drop DPmax is reached. The maximum admissible pressure drop DPmax is generally confirmed when the reactors are put into service for the first time. In the case of a heavy fraction hydrotreatment process, the limit value of the maximum admissible pressure drop or pressure drop DPmax is generally between 0.3 and 1 MPa (3 and 10 bar), preferably between 0 , 5 and 0.8 MPa (5 and 8 bars).

The process according to the invention is a process for catalytic hydrotreatment of a heavy fraction of hydrocarbons generally containing asphaltenes, sediments, sulfur, nitrogenous and metallic impurities, in the presence of hydrogen, comprising a preliminary hydrodetallation stage. by means of a guard zone comprising at least two permutable reactors in a fixed bed, each comprising at least one catalytic fixed bed, which are used cyclically according to the following steps:

a) a step in which at least two reactors are used in series in downward flow until reaching a pressure drop threshold DPi whose value is between 20 and 70% of the maximum allowable pressure drop,

b) a step of inverting the direction of flow and placing said at least two reactors in parallel for a duration at most equal to the clogging time of the first reactor brought into contact with the feed, until reaching the maximum admissible pressure drop DPmax.

c) a step during which the said clogged first reactor is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) is not still clogged (s) operate in downflow,

d) a step during which said at least two reactors are used in series, the reactor whose catalyst was regenerated during the previous step being reconnected and said step being continued for a duration at most equal to a fraction of the time of clogging of the second reactor brought into contact with the load, corresponding to reaching a pressure drop threshold DPi whose value is between 20 and 70% of the maximum allowable pressure drop DPmax,

e) a step of reversing the direction of flow and placing the two reactors in parallel, for a period at most equal to the clogging time of the second reactor brought into contact with the load until the loss is reached maximum permissible load DPmax

f) a step during which said clogged second reactor is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) is not still clogged (s) operate in downflow; said steps a), b), c), d), e), f) can be repeated cyclically in this order.

During the transition to updraft, during steps b) and e) (Up flow), the two reactors are in parallel, the flow is divided. In all other cases (series reactors: stages a) and d) or single reactor in the case of an intervention on the second reactor: stages c) and f)), the direction of flow is in downdraft flow).

Depending on the initial configuration (load flow rate, nature of the load, etc.), the up flow switch may involve, on the one hand, the addition of two-phase distribution internals at the bottom of each reactor and the addition of internal type grids at the top of the reactor to prevent possible expansion of the bed.

Charges

The feedstock treated in the hydrotreatment process according to the invention is advantageously a hydrocarbon feedstock having an initial boiling temperature of at least 340 ° C and a final boiling temperature of at least 440 ° C. Preferably, its initial boiling temperature is at least 350 ° C, preferably at least 375 ° C, and its final boiling temperature is at least 450 ° C, preferably at least 460 ° C, more preferably at least 500 ° C, and even more preferably at least 600 ° C.

The hydrocarbon feedstock according to the invention can be chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, headless crude oils, deasphalting resins, deasphalting asphalts or pitches, residues from processes conversion, aromatic extracts from base production chains for lubricants, oil sands or their derivatives, oil shales or their derivatives, mother rock oils or their derivatives, taken alone or as a mixture. In the present invention, the charges which are treated are preferably atmospheric residues or residues under vacuum, or mixtures of these residues.

The hydrocarbon feedstock treated in the process may contain, among other things, sulfur impurities. The sulfur content may be at least 0.1% by weight, preferably at least 0.5% by weight, preferably at least 1% by weight, more preferably at least 2% by weight .

The hydrocarbon feedstock treated in the process may contain inter alia metallic impurities, in particular nickel and vanadium. The sum of the nickel and vanadium contents is generally at least 10 ppm, preferably at least 50 ppm, preferably at least 100 ppm.

These charges can advantageously be used as such. Alternatively, they can be diluted by a co-charge. This co-charge can be a hydrocarbon fraction or a mixture of lighter hydrocarbon fractions, which can preferably be chosen from products resulting from a catalytic cracking process in a fluid bed (FCC or "Fluid Catalytic Cracking" according to English terminology). Saxon), a light cut (LCO or "light cycle oil" according to the English terminology), a heavy cut (HCO or "heavy cycle oil" according to the English terminology), a decanted oil, an FCC residue, a diesel fraction, in particular a fraction obtained by atmospheric distillation or under vacuum, such as for example vacuum diesel, or can also come from another refining process such as coking or visbreaking.

The co-charge can also advantageously be one or more cuts resulting from the liquefaction process of coal or biomass, aromatic extracts, or any other hydrocarbon cuts, or else non-petroleum fillers such as pyrolysis oil. The heavy hydrocarbon feedstock according to the invention can represent at least 50%, preferably 70%, more preferably at least 80%, and even more preferably at least 90% by weight of the total hydrocarbon feedstock treated by the process according to the invention.

Operating conditions

The hydrotreatment process according to the invention, and more particularly the prior hydrodemetallization step of the process according to the invention, can advantageously be carried out at a temperature between 320 ° C and 430 ° C, preferably 350 ° C at 410 ° C., under a partial hydrogen pressure advantageously between 3 MPa and 30 MPa, preferably between 10 and 20 MPa, at a space velocity (WH) advantageously between 0.05 and 5 volume of charge per volume of catalyst and per hour, and with a gaseous hydrogen to liquid hydrocarbon charge ratio advantageously between 200 and 5000 normal cubic meters per cubic meter, preferably 500 to 1500 normal cubic meters per cubic meter.

In the preliminary hydrodetallization stage, the value of the WH of each reactor which can be switched in operation is preferably between 0.5 and 4 volumes of catalyst per volume of feed per hour, and most often between 1 and 2 volume of catalyst per volume of feed per hour. The overall WH value of the swappable reactors and that of each reactor is chosen by a person skilled in the art so as to achieve the maximum hydrodemetallization (HDM) while controlling the reaction temperature (limitation of exothermicity).

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The catalysts used in the hydrotreatment process according to the invention, and in particular in the permutable guard reactors, are preferably known hydrotreatment catalysts and are generally granular catalysts comprising, on a support, at least one metal or compound of metal having a hydrodehydrogenating function. These catalysts are advantageously catalysts comprising at least one metal from group VIII, generally chosen from the group formed by nickel and / or cobalt, and / or at least one metal from group VIB, preferably molybdenum and / or tungsten . The support used is generally chosen from the group formed by alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals.

Prior to injection of the feed, the catalysts used in the process according to the present invention are preferably subjected to a sulfurization treatment making it possible to transform, at least in part, the metallic species into sulfide before they are brought into contact with the feed. treat. This activation treatment by sulfurization is well known to those skilled in the art and can be carried out by any method already described in the literature either in situ, that is to say in the reactor, or ex situ.

The system of permutable guard zones with reversal of the direction of flow and parallelization of the permutable reactors making it possible to carry out a prior hydrodetallization of the charge advantageously precedes a hydrotreating section of heavy hydrocarbon charges in a fixed bed or bubbling bed.

Preferably, it precedes a hydrotreating section comprising at least one hydrodemetallization unit and at least one hydrodesulfurization unit. The swappable reactors are preferably integrated upstream of the hydrodemetallization unit, the swappable reactors being used as guard beds.

The hydrotreatment process according to the invention advantageously makes it possible to carry out 50% and more of hydrodemetallization of the feedstock at the outlet of the permutable reactors, and more preferably of 50 to 95% of hydrodemetallization), thanks to the speed hourly volume chosen WH and the efficiency of the HDM hydrodemetallization catalyst.

In the case shown in FIG. 1, the load 1 arrives in the permutable reactor (s) through line 1 and leaves this or these reactors through line 13. The load leaving the guard reactor (s) arrives via line 13 in the hydrotreating section 14 and more precisely in the HDM hydrodemetallization unit 15 comprising one or more reactors. The effluent from the HDM hydrodemetallization unit 15 is withdrawn through line 16, then sent to the HDT hydrotreating unit 17 comprising one or more reactors. The final effluent is drawn off via line 18.

Modes of realization

It is possible to put several swappable reactors upstream, their number being strictly greater than 2, with change of direction on two or more of them.

According to one embodiment, illustrated in FIG. 3, at least one of the permutable reactors comprises at least two catalytic beds. In this configuration, it may be advantageous to short-circuit the upper layer, which has undergone most of the clogging, during the updraft steps. The short-circuiting of a clogged bed can be carried out externally by a lateral draw-off and a short-circuit line, comprising a valve. It is thus possible for steps b) and / or e) to “short-circuit” the catalytic beds already clogged, and to remove the effluent from this reactor by a pipe situated between the catalytic beds in the case of two beds catalytic or between a bed i and a bed i + 1 in the case where the reactor comprises n catalytic beds, i being an integer ranging from 1 to n. Advantageously, i + 1 denotes the first clogged bed in the direction of flow, the reaction effluent therefore leaves the reactor just before the flow has encountered the clogged zone. This embodiment allows optimal use of the overall catalytic volume, since the flow does not cross the already clogged part of the reactor.

In a preferred variant of this embodiment, all of the swappable reactors comprise at least two catalytic beds. In this configuration, it is possible for both steps b) and e) to remove the effluent from the reactor being clogged by a pipe located between the catalytic beds in the case of two catalytic beds or between a bed i and a bed i + 1 in the case where the reactor comprises n catalytic beds, i being an integer ranging from 1 to n.

In an even more preferred variant, the guard zone comprises two interchangeable reactors each comprising two catalytic beds. In this configuration, it is possible for both steps b) and e) to remove the effluent from the reactor being clogged by a lateral withdrawal between the two catalytic beds, just before the already clogged catalytic zone.

Description of the figures

Figure 1: Switchable reactor system according to the prior art

The operation of the swappable reactors according to FR2681871 is described in FIG. 1 comprising two guard zones (or swappable reactors) R1a and R1 b. This process comprises a series of cycles, each comprising four successive stages:

a first step (hereinafter referred to as step a) during which the charge successively passes through the reactor R1 a, then the reactor R1b,

a second step (hereinafter referred to as step b) during which the charge passes only through the reactor R1b, the reactor R1a being short-circuited for regeneration and / or replacement of the catalyst,

a third step (hereinafter referred to as step c) during which the charge successively passes through the reactor R1b, then the reactor R1a,

a fourth step (hereinafter referred to as step d) during which the charge passes only through the reactor R1a, the reactor R1b being short-circuited for regeneration and / or replacement of the catalyst.

During step a) of the process, the charge is introduced through line 3 and line 21 comprising a valve V1 open towards line 21 'and the guard reactor R1a containing a fixed bed A of catalyst. During this period the valves V3, V4 and V5 are closed. The effluent from reactor R1a is sent via line 23, line 26 comprising an open valve V2 and line 22 'in the guard reactor R1 b containing a fixed bed B of catalyst. The effluent from reactor R1 b is sent via lines 24 and 24 'comprising an open valve V6 and line 13 to the main hydrotreatment section 14. During step b) of the process, valves V1, V2, V4 and V5 are closed and the charge is introduced via line 3 and line 22 comprising a valve V3 open towards line 22 'and the reactor R1 b. During this period the effluent from reactor R1 b is sent via lines 24 and 24 'comprising an open valve V6 and line 13 to the main hydrotreatment section 14. During step c) valves V1, V2 and V6 are closed and the valves V3, V4 and V5 are open. The charge is introduced via line 3 and lines 22 and 22 'to the reactor R1 b. The effluent from reactor R1 b is sent through line 24, line 27 comprising an open valve V4 and line 21 'in the guard reactor RI a. The effluent from reactor R1a is sent via lines 23 and 23 ′ comprising an open valve V5 and line 13 to the main hydrotreatment section 14. In step d) the valves V2, V3, V4 and V6 are closed and valves V1 and V5 are open. The charge is introduced via line 3 and lines 21 and 21 'to the reactor R1 a. During this period the effluent from reactor R1 a is sent via lines 23 and 23 'comprising an open valve V5 and line 13 to the main hydrotreating section 14. The cycle then begins again. The operations on the valves of unit 30 allowing the operation of the permutable reactors according to FR2681871 are reported in Table 1.

Table 1: Operations on the valves around the swappable reactors according to FR2681871

Cycle Stage Intervention V1 V2 V3 V4 V5 V6 at R1A + R1B O * O p ** F F O b R1B R1A F F O F F O vs R1B + R1A F F O O O F d R1A R1B O F F F O F at R1A + R1B O O F F F O

* O = open, ** F = closed

Figure 2: System according to the invention

The operation of the system of swappable reactors according to the invention is described without limitation in FIG. 2 comprising two guard zones (or swappable reactors) R1a and R1 b. This process comprises a series of cycles each comprising six successive stages:

- a first step (hereinafter referred to as step a) during which the charge successively passes through the reactor R1 a, then the reactor R1 b, placed in series, the flow is descending; until reaching a pressure drop of between 20 and 70% of the maximum admissible pressure drop by the DPmax equipment, preferably between 30 and 60% of DPmax, even more preferably between 35 and 50% of DPmax;

a second step (hereinafter referred to as step b) of inverting the direction of flow and placing the reactors R1a and R1b in parallel for a period at most equal to the clogging time of R1a, determined by reaching the maximum pressure drop admissible by the reactors, the load then passes simultaneously through the reactor R1 b and the reactor R1 a, the flow is ascending,

a third step (hereinafter called step c ") during which said (first) clogged reactor R1a is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor not yet clogged R1b is operating, the load passes only through the RIB reactor in a descending manner.

a fourth step (hereinafter referred to as step d) during which the first reactor R1A is put back into operation, R1B and R1A operate in series in downward flow

- a fifth step (hereinafter referred to as step e ") during which the direction of flow is reversed, R1A and R1B operate in parallel in ascending current

- a sixth stage (hereinafter referred to as stage f ") during which said (second) clogged reactor R1B is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor not yet clogged R1A is operating, the load passes only through the reactor R1A in a descending manner, the reactor R1B being short-circuited for regeneration and / or replacement of the catalyst

A new cycle can begin, again with step a): R1B is put back into operation, R1A and R1B operate in series in downflow.

In the method according to the invention, illustrated by FIG. 2, during step a) of the method, the load 1 is introduced by line 3 and line 21 comprising a valve V1 open towards line 21 'and the guard reactor R1a containing a fixed bed A of catalyst. During this period the valves V3, V4 and V5, V8 and V9 are closed. The effluent from reactor R1a is sent via line 23, line 26 comprising an open valve V2 and line 22 'in the guard reactor R1 b containing a fixed bed B of catalyst. The effluent from reactor R1 b is sent via lines 24 and 24 'comprising an open valve V6 and via line 13 comprising a valve V10 open towards the main hydrotreating section 14. The flow takes place in a downward flow.

During stage b) of the process, the direction of flow is reversed to pass in ascending flow, the valves V1, V2, V3 and V4 as well as V10 and V11 are closed and the load is introduced simultaneously in ascending current:

- by line 3 and line 28 comprising an open V7 valve and line 23 'comprising an open valve V5 to line 23 and the reactor R1 A

- by line 3 and line 28 comprising an open valve V7 and line 24 'comprising an open valve V6 to line 24 and the reactor R1 B.

During this period the effluent from reactor R1 b is sent via lines 22 'and 30 comprising an open valve V9 and line 31 to the main hydrotreatment section 14. The effluent from reactor R1 a is sent through lines 22 'and 30 comprising an open valve V8 and the pipe 31 to the main hydrotreating section 14.

During step c) the valves V1, V2, V4, V5, V7, V8, V9 are closed and the valves V3, V6, V10, and V11 are open. The charge is introduced via line 3 and lines 22 and 22 'to the reactor R1 b. The effluent from reactor R1b is sent via lines 24 and 24 'comprising an open valve V6 and line 13 comprising a valve V10 open towards the main hydrotreating section 14.

The clogged R1a reactor is thus short-circuited to allow intervention on the R1a reactor to replace / reload the catalyst.

During step d) the valves V1, V2, V6, V7, V8, V9 are closed and the valves V3, V4, V5, V10 and V11 are open. The charge is introduced via line 3 and lines 22 and 22 'to the reactor R1 b, the valves V3 and V11 being open. During this period the effluent from reactor R1 b is sent through lines 24 and 27 ’comprising an open valve V4 and line 21’ to reactor R1a. The effluent from reactor R1 a is sent via a line 23 comprising an open valve V5 and an open valve V10 to the main hydrotreatment section 14. The flow takes place in a descending manner in the reactors R1b and R1a placed in series.

During step e), the direction of flow is reversed to pass in upward flow, the valves V1, V2, V3 and V4 as well as V10 and V11 are closed and the load is introduced simultaneously in upward current:

- by line 3 and line 28 comprising an open valve V7 and line 23 'comprising an open valve V5 to line 23 and the reactor R1 a.

- by line 3 and line 28 comprising an open V7 valve and line 24 ’comprising an open valve V6 to line 24 and the reactor R1 b.

During this period the effluent from reactor R1 b is sent via lines 22 'and 30 comprising an open valve V9 and line 31 to the main hydrotreatment section 14. The effluent from reactor R1 a is sent through lines 22 'and 30 comprising an open valve V8 and the pipe 31 to the main hydrotreating section 14.

During step f), the valves V2, V3, V4, V6, V7, V8, V9 are closed and the valves V1, V5, V10, and V11 are open. The charge is introduced via line 3 and lines 21 and 21 'to the reactor R1 a. The effluent from the reactor R1a is sent via the lines 23 and 23 ′ comprising an open valve V5 and the line 13 comprising a valve V10 open to the main hydrotreatment section 14. The clogged reactor R1b is thus short-circuited in order to allow intervention on the RRIb reactor to replace / reload the catalyst.

The cycle then begins again. The operations on the valves of the unit allowing the operation of the swappable reactors according to the invention are reported in Table 2.

Table 2: Operations on the valves around the switchable reactors according to the invention

Step Cycle Flow direction Intervention V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 at R1A + R1B Descending 0 * 0 F “ F F 0 F F F 0 0 b R1A + R1B Ascending F F F F 0 0 0 0 0 F F vs R1B Descending R1A F F 0 F F 0 F F F 0 0 d R1B + R1A Descending F F 0 0 0 F F F F 0 0 e R1A + R1B Ascending F F F F 0 0 0 0 0 F F f R1A Descending R1B 0 F F F 0 F F F F 0 0 at R1A + R1B Descending 0 0 F F F 0 F F F 0 0

* O = open, ** F = closed

Figure 3: Embodiment with short circuit

In this embodiment, FIG. 3 illustrates a short-circuiting of the catalytic bed already clogged during steps b) and e).

During step a) of the process, the charge 1 is introduced through line 3 and line 21 comprising a valve V1 open towards line 21 'and the guard reactor R1a containing a fixed bed A of catalyst. During this period the valves V3, V4 and V5, V8, V9, V12, V13 are closed. The effluent from reactor R1 a is sent via line 23, line 26 comprising an open valve V2 and line 22 ′ in the guard reactor R1 b containing a fixed bed B of catalyst. The effluent from reactor R1 b is sent via lines 24 and 24 'comprising an open valve V6 and via line 13 comprising a valve V10 open towards the main hydrotreating section 14. The flow takes place in a downward flow.

During stage b) of the process, the direction of flow is reversed to pass in ascending flow, the valves V1, V2, V3 and V4 as well as V10, V11, and V13 are closed and the load is introduced simultaneously in updraft:

- by line 3 and line 28 comprising an open V7 valve and line 23 'comprising an open valve V5 to line 23 and the reactor R1 A

- by line 3 and line 28 comprising an open V7 valve and line 24 ’comprising an open valve V6 to line 24 and the reactor R1 B.

During this period, the effluent from reactor R1 b is sent via lines 22 ’and 30 comprising an open valve V9 and line 31 to the main hydrotreating section 14.

The effluent from reactor R1 a is sent via lines 32 and 30 comprising an open valve V12 and line 31 to the main hydrotreating section 14. Valve V8 is closed. The already clogged catalytic bed is thus short-circuited.

During step c) the valves V1, V2, V4, V5, V7, V8, V9, V12, V13 are closed and the valves V3, V6, V10, and V11 are open. The charge is introduced via line 3 and lines 22 and 22 'to the reactor R1 b. The effluent from reactor R1b is sent via lines 24 and 24 'comprising an open valve V6 and line 13 comprising a valve V10 open towards the main hydrotreating section 14. The blocked reactor R1a is thus short-circuited in order to allow intervention on the R1a reactor to replace / reload the catalyst.

During step d) the valves V1, V2, V6, V7, V8, V9, V12, V13 are closed and the valves V3, V4, V5, V10 and V11 are open. The charge is introduced via line 3 and lines 22 and 22 'to the reactor R1 b, the valves V3 and V11 being open. During this period the effluent from reactor R1 b is sent via lines 24 and 27 'comprising an open valve V4 and line 21' to reactor R1a. The effluent from reactor R1a is sent via a line 23 comprising an open valve V5 and an open valve V10 to the main hydrotreatment section 14. The flow takes place in a descending manner in the reactors R1b and R1a placed in series.

During step e), the direction of flow is reversed to pass in ascending flow, the valves V1, V2, V3 and V4 as well as V10, V11 and V12 are closed and the load is introduced simultaneously in ascending current:

- by line 3 and line 28 comprising an open valve V7 and line 23 'comprising an open valve V5 to line 23 and the reactor R1 a.

- by line 3 and line 28 comprising an open valve V7 and line 24 'comprising an open valve V6 to line 24 and the reactor R1 b.

During this period the effluent from reactor R1 b is sent via lines 33 and 30 comprising an open valve V13 and line 31 to the main hydrotreating section 14. The effluent from reactor R1 a is sent through lines 22 ' and 30 comprising an open valve V8 and the pipe 31 to the main hydrotreating section 14.

During step f), the valves V2, V3, V4, V6, V7, V8, V9, V12, V13 are closed and the valves V1, V5, V10, and V11 are open. The charge is introduced via line 3 and lines 21 and 21 'to the reactor R1 a. The effluent from the reactor R1a is sent via the lines 23 and 23 ′ comprising an open valve V5 and the line 13 comprising a valve V10 open to the main hydrotreatment section 14. The clogged reactor R1b is thus short-circuited in order to allow intervention on the RRIb reactor to replace / reload the catalyst.

The cycle then begins again. The operations on the valves of the unit allowing the operation of the swappable reactors according to the invention are reported in Table 3.

Step Cycle Direction of traffic Int. V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 at R1A + R1B Descending - 0 * 0 F ” F F 0 F F F 0 0 F F b R1A + R1B Ascending - F F F F 0 0 0 F 0 F F 0 F vs R1B Descending R1A F F 0 F F 0 F F F 0 0 F F d R1B + R1A Descending - F F 0 0 0 F F F F 0 0 F F e R1A + R1B Ascending - F F F F 0 0 0 0 F F F F 0 f R1A Descending R1B 0 F F F 0 F F F F 0 0 F F at R1A + R1B Descending - 0 0 F F F 0 F F F 0 0 F F

Examples

The examples below illustrate the invention without limitation.

Example 1 (comparative, not in accordance with the invention, according to FR2681871)

The feedstock consists of a mixture (70/30% wt) of atmospheric residue (RA) of Middle East origin (Arabian Medium) and of a vacuum residue (VR) of Middle East origin (Arabian Light). This mixture is characterized by a high viscosity (0.91 cP) at ambient temperature, a density of 994 kg / m ³ , high contents of Conradson carbon (14% by weight) and asphaltenes (6% by weight) and a high quantity of nickel (22 ppm by weight), vanadium (99 ppm by weight) and sulfur (4.3% by weight).

The hydrotreatment process is carried out according to the process described in FR2681871 and includes the use of two permutable reactors (R1A and R1B in Figure 1). The two reactors are loaded with an HDM CoMoNi / alumina hydrodemetallization catalyst. A cycle is defined as integrating steps from a) to d) (cf. table 1). The deactivation and / or clogging time is reached when the pressure drop reaches 0.7 MPa (7 bars) and / or the average bed temperature reaches 405 ° C and / or when the temperature difference on a bed catalytic becomes radially higher than 5 ° C.

The process is carried out under a pressure of 19 MPa, a temperature at the start of the cycle of 360 ° C and at the end of the cycle of 400 ° C, and a WH = 2 h ¹ per reactor allowing a rate of demetallation close to 60 to be maintained. %.

Figure 4 shows the evolution of the cycles in terms of operating time (in days) for the process according to FR2681871. A cycle being defined here as the alternative operation of R1a then R1b. Thus, according to FIG. 4, the curve of the reactor R1a according to the state of the art (basic case R1a) shows at the start of the cycle an increase in the pressure drop in the first reactor R1a up to its maximum admissible value ( DPmax = 0.7 MPa or 7 bars) from which the catalyst must be replaced. In the case of the state of the art (FR2681871), the operating time of the reactor R1 a is therefore 210 days. When replacing the catalyst in reactor R1 a, the pressure drop in reactor R1b reached approximately 3 bars. During the next phase where the charge passes through the reactor R1b, then the reactor R1a containing a new catalyst, the pressure drop of the reactor R1b increases to the maximum admissible value, which is reached after 320 days of operation. A second cycle can be envisaged on these permutable reactors, by replacing the catalyst of reactor R1 b.

The deactivation and / or clogging time (or the operating time) of the first zone is therefore 210 days. In total, we observe a cycle time of 320 days for the first cycle and 627 days for two cycles.

It is recalled that at the end of the operating cycle, the process is stopped to replace the catalyst.

Example 2 (according to the invention)

The hydrotreatment process is repeated with the same charge, the same catalyst and under the same operating conditions according to Example 1. The rate of HDM hydrodemetallization is maintained at 60%.

The diagram used for the example is that presented in FIG. 2. FIG. 4 shows that according to the prior art, the cycle duration is 320 days for the first cycle. Indeed, the pressure loss increases in the catalytic bed until reaching the maximum admissible pressure loss DPmax for the equipment installed in this example of 0.7 MPa (7 bar) after 210 days for the first reactor and 320 days for the second.

On the other hand, by integrating the inversion and parallelization step of the direction of flow according to the invention when the pressure drop reaches a threshold Dpi equal to 0.3 MPa (3 bar), or approximately 43% from the maximum admissible pressure drop in DPmax equipment (Figure 5), the service life for the first reactor is extended to 380 days, for a cycle time of 580 days. It therefore appears in this example that the hydrotreatment process incorporating a step of changing the direction of flow and placing the reactors in parallel makes it possible to significantly increase the cycle time of the catalytic hydrodemetallization zone, in particular with a gain of 260 days (or 80%).

Claims (15)

1. A process for the catalytic hydrotreatment of a heavy hydrocarbon feedstock, in the presence of hydrogen, comprising a preliminary hydrodemetallization stage by means of at least two permutable reactors in a fixed bed each comprising at least one catalytic bed, which are used cyclically according to the following steps: a) a step in which at least two reactors are used in series in downward flow until reaching a pressure drop threshold Dpi of value between 20 and 70% of the maximum admissible pressure drop DPmax, b) a step of reversing the direction of flow and placing said at least two reactors in parallel until the maximum admissible pressure drop DPmax is reached c) a stage during which the first reactor brought into contact with the feed in stage a) is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) not yet clogged (s) operate in downflow, d) a step during which said at least two reactors are used in series, the reactor whose catalyst was regenerated during the previous step being reconnected and said step being continued until a loss threshold is reached Dpi load value between 20 and 70% of the maximum admissible pressure drop DPmax, e) a step of reversing the direction of flow and placing the two reactors in parallel, until the maximum admissible pressure drop DPmax is reached f) a stage during which the second reactor brought into contact with the feed in stage a) is short-circuited and the catalyst which it contains is regenerated and / or replaced by fresh catalyst, the direction of flow is modified and only the reactor (s) not yet clogged (s) operate in downflow; said steps a), b), c), d), e), f) can be repeated cyclically in this order. 2. Method according to claim 1 wherein at least one of the reactors comprises n catalytic beds and the effluent from said reactor is removed in steps b) and / or e) by a lateral withdrawal between a catalytic bed i and a catalytic bed i +1, n being an integer greater than or equal to 2, i being an integer ranging from 1 to n. 3. Method according to claim 2 wherein said catalytic bed i + 1 denotes the first catalytic bed clogged in the direction of flow. 4. Method according to claim 2 or 3 wherein said at least two permutable reactors all comprise at least two catalytic beds. 5. Method according to one of claims 1 to 4 wherein the pressure drop threshold Dpi has a value between 30 and 60% of the maximum allowable pressure drop DPmax. 6. The method of claim 5 wherein the pressure drop threshold Dpi has a value between 35 and 50% of the maximum allowable pressure drop DPmax. 7. Method according to one of the preceding claims, in which the heavy hydrocarbon feedstock has an initial boiling temperature of at least 340 ° C and a final boiling temperature of at least 440 ° C. 8. The method of claim 7 wherein the charge is selected from atmospheric residues, vacuum residues from direct distillation, crude oils, headless crude oils, deasphalt resins, asphalt or deasphalting pitches, residues from conversion processes, aromatic extracts from base production chains for lubricants, oil sands or their derivatives, oil shales or their derivatives, mother rock oils or their derivatives, taken alone or as a mixture. 9. The method of claim 8 wherein the charge is chosen from atmospheric residues or vacuum residues, or mixtures of these residues. 10. Method according to one of the preceding claims implemented at a temperature between 320 ° C and 430 ° C, under a partial hydrogen pressure between 3 MPa and 30 MPa, at a space velocity (WH) between 0 , 05 and 5 charge volume per catalyst volume and per hour, and with a gaseous hydrogen to liquid hydrocarbon charge ratio of between 200 and 5000 normal cubic meters per cubic meter. 11. The method of claim 10 in which the prior hydrodemetallization step is carried out in the presence of a hydrodemetallization catalyst comprising at least one metal from group VIII, and / or at least one metal from group VIB, on a support used chosen from the group formed by alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. 12. The method of claim 11 in which the prior hydrodemetallization step is carried out at a space speed WH of each reactor which can be switched in operation between 0.5 and 4 volume of charge per volume of catalyst and per hour. 13. The method of claim 12 wherein the prior hydrodemetallization step is carried out at a space speed WH of each reactor which can be switched in operation between 1 and 2 volume of feed per volume of catalyst and per hour. 14. Method according to one of the preceding claims, in which the maximum admissible pressure drop DPmax is between 0.3 and 1 MPa. 15. The method of claim 14 wherein the maximum allowable pressure drop DPmax is between 0.5 and 0.8 MPa. 1/5