FR3000097A1 - INTEGRATED PROCESS FOR THE TREATMENT OF PETROLEUM LOADS FOR THE PRODUCTION OF LOW SULFUR CONTENT FIELDS - Google Patents

Abstract

The present invention relates to a process for the treatment of heavy petroleum feedstocks for the production of fuel oils and oil bases, in particular bunker fuels and bunker oil bases, with a low sulfur content. This process comprises a step (a) of fixed-bed hydrotreating of a sulfur-containing heavy hydrocarbon feedstock, followed by a hydroconversion step (b) in a reactor containing a bubbling-bed supported catalyst, and a step (c). separating the effluent from step (b) to obtain at least one gaseous fraction and at least said liquid hydrocarbon fraction, without intermediate separation step between step (a) of hydrotreating and step (b) ) hydroconversion.

Description

FIELD OF THE INVENTION The present invention relates to the refining and conversion of heavy hydrocarbon fractions containing, inter alia, sulfur-containing impurities. It relates more particularly to a process for the treatment of heavy petroleum feedstocks for the production of fuel oils and oil bases, in particular bunker oil and bunker oil bases with low sulfur content. TECHNOLOGICAL BACKGROUND While regulations on sulfur content in land-based fuels, typically gasoline and diesel, had become very stringent in recent decades, regulations on sulfur content in marine fuels so far as not binding. Indeed, marine fuels currently on the market can contain up to 3.5% or 4.5% by weight of sulfur. As a result, ships have become the main source of sulfur dioxide emissions (802).

In order to reduce these emissions, the International Maritime Organization (IMO) has submitted recommendations in terms of specifications for marine fuels (Annex VI of the MARPOL Convention). These recommendations are presented in the 2012 version of ISO 8217. The recommendations now focus on SO 'emissions from marine fuels. The equivalent sulfur content recommended by 2020 or 2025 is less than or equal to 0.5% by weight for vessels operating outside the "Sulfur Emission Control Areas" (ZCES or SECA, "Sulfur Emission Control Areas "according to the English terminology). Within the SECAs, the IMO predicts an equivalent sulfur content of 0.1% or less by 2015.

In addition, another very restrictive recommendation concerns the sediment content after aging according to ISO 10307-2 which must be less than or equal to 0.1%. The applicant has set itself the objective of producing fuel oils and fuel oil bases, in particular bunker oil and bunker oil bases, in accordance with the recommendations of the MARPOL Convention in terms of equivalent sulfur content, and preferably respecting also recommendations on sediment content after aging. Fuel oils used in maritime transport generally include atmospheric distillates, vacuum distillates, atmospheric residues and vacuum residues from direct distillation or from refining processes, including hydrotreatment and conversion processes, which may be be used alone or mixed. One of the objectives of the present invention is to propose a process for converting heavy petroleum feedstocks for the production of fuel oils and oil bases, in particular bunker oils and bunker oil bases, with very low sulfur content. Another object of the present invention is to produce jointly, by means of the same process, atmospheric distillates (naphtha, kerosene, diesel), vacuum distillates and / or light (C 1 to C 4) gases. The bases of the naphtha and diesel type can be upgraded to refineries for the production of automotive and aviation fuels, such as, for example, super-fuels, Jet fuels and gas oils.

Methods for refining and converting heavy petroleum feedstocks comprising a first fixed bed hydrotreatment stage and then a bubbling bed hydroconversion stage have been described in patent documents FR 2764300, CA 1238005, EP 1343857 and EP 0665282. EP 0665282, which describes a process for the hydrotreatment of heavy oils, aims to extend the life of the reactors. CA 1238005 describes a process for converting a heavy liquid hydrocarbon feedstock using a plurality of reactors in series, wherein the conversion rate is improved by special recycling of the heavy fraction obtained. The method described in FR 2764300 aims in turn to obtain not fuel bases, including bunker oil bases, but fuels (gasoline and diesel) having in particular a low sulfur content. In addition, the feedstocks treated in this process contain little or no asphaltenes. Finally, the process disclosed in EP 1343857 is described as a hydrotreatment process that can implement a hydrodemetallation section, which can be preceded by a guard zone of type reactive reactors, and a hydrodesulfurization section. None of these documents describe the production of a fuel oil or ultra-low sulfur fuel oil base that meets the new recommendations of the International Maritime Organization, and low sediment content as required by the new version of ISO 8217. : 2012. One of the objectives of the present invention is to adapt and improve the conversion methods described in the state of the art for the production of fuel oils and oil bases including low sulfur content.

BRIEF DESCRIPTION OF THE INVENTION The research work led the Applicant to discover that, surprisingly, an improvement of the existing processes in terms of the production of fuel bases and in terms of the quality of said fuel oil bases, in particular of sulfur content and sediment content, is possible by a combination of different stages, chained in a specific way. The subject of the invention is, first of all, a process for treating a hydrocarbon feedstock having a sulfur content of at least 0.5% by weight, an asphaltene content of at least 2% by weight, a initial boiling point of at least 340 ° C and a final boiling point of at least 440 ° C, to obtain at least one liquid hydrocarbon fraction having a sulfur content of less than or equal to 0.5% by weight, comprising the following successive stages: a) a fixed bed hydrotreatment stage, in which the hydrocarbon feedstock and hydrogen are brought into contact on at least one hydrotreatment catalyst, b) a hydroconversion stage at least a portion of the effluent from step (a) in at least one reactor containing a catalyst supported in bubbling bed, and c) a step of separating the effluent from step (b) to obtain at least a gaseous fraction and at least said liquid hydrocarbon fraction without an intermediate separation step between the hydrotreatment step (a) and the hydroconversion step (b).

The invention also relates to the fuel oil used in maritime transport, obtained from such a process, having a sulfur content of less than or equal to 0.5% by weight, preferably less than or equal to 0.1% by weight. .

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 represents an embodiment of the method according to the invention without intermediate separation of the product between the fixed bed section and the bubbling bed section. FIG. 2 represents in larger, for more legibility, the guard zones of the hydrotreatment section of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION It is stated that, throughout this description, the expression "understood (e) between ... and ..." should be understood as including the limits cited. The method according to the invention therefore comprises a first step (a) of hydrotreating in a fixed bed, followed by a step (b) of bubbling bed hydroconversion, and finally a step (c) of separation. The goal of hydrotreating is both to refine, that is to say to significantly reduce the content of metals, sulfur and other impurities, while improving the hydrogen-to-carbon ratio (HIC) and while transforming the hydrocarbon feed more or less partially in lighter cuts. The effluent obtained in the fixed-bed hydrotreating step (a) is then directly sent to the boiling-bed hydroconversion stage (b) which partially converts the hydrocarbon effluent obtained at the end of the boiling point. hydrotreating step (a) in order to produce an effluent which may advantageously be used wholly or partly as fuel oil or as fuel oil base, especially as bunker oil or bunker oil base. One of the interests of the sequence of a hydrotreatment in a fixed bed and then a hydroconversion in a bubbling bed lies in the fact that the charge of the bubbling bed hydroconversion reactor is already at least partially hydrotreated. In this way, it is possible to obtain equivalent conversion of hydrocarbon effluents of better quality, in particular with lower sulfur contents. In addition, the catalyst consumption in the bubbling bed hydroconversion reactor is greatly reduced compared to a process without prior fixed bed hydrotreating. On the other hand, the process according to the invention is characterized in that it does not comprise an intermediate separation step between the hydrotreatment step (a) and the hydroconversion stage (b). Directly sending the effluent from the fixed-bed hydrotreatment step into the boiling-bed hydroconversion stage without a separation step has several advantages, in particular: the process has a better thermal integration since the temperature effluent at the outlet of the fixed hydrotreatment bed is preserved. This does not exclude the fact that the effluent temperature of the fixed bed hydrotreatment step can be controlled and adjusted before the bubbling bed hydroconversion step. - The process has a better energy efficiency since there is no significant pressure drop between the output of the fixed bed hydrotreating section and the inlet of the bubbling bed hydroconversion section. The device making it possible to implement the process, and more particularly the elements necessary for the recycling of hydrogen in the process, can be simplified. Indeed, in the absence of intermediate separation, a single hydrogen recirculation loop common to the fixed bed hydrotreatment section and the bubbling bed hydroconversion section is necessary since there is no need for intermediate separation. evacuation of a hydrogen-rich gas at the end of the fixed-bed hydrotreating step. A single compressor is sufficient, and the size of this compressor can be reduced to the extent that the flow of recycled gas is also lower. The process according to the invention advantageously makes it possible to produce light fractions, fuel oils and oil bases, in particular for marine use, with a low sulfur content, with a high efficiency and energy efficiency, from a feedstock. heavy hydrocarbon sulfur. The Hydrocarbon Feed The hydrocarbon feedstock treated in the process according to the invention can be described as a heavy feedstock. It has an initial boiling point of at least 340 ° C and a final boiling temperature of at least 440 ° C. Preferably, its initial boiling point is at least 350 ° C., preferably at least 375 ° C., and its final boiling point is at least 450 ° C., preferably at least 460 ° C. C, more preferably at least 500 ° C, and even more preferably at least 600 ° C. The hydrocarbon feedstock may be chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, crude head oils, deasphalting resins, asphalts or deasphalting pitches, residues resulting from conversion processes, aromatic extracts from lubricant base production lines, oil sands or derivatives thereof, bituminous shales or derivatives thereof, parent rock oils or their derivatives, alone or in admixture. In the present invention, the fillers being treated are preferably atmospheric residues or vacuum residues, or mixtures of these residues.

The hydrocarbon feedstock treated in the process according to the invention is sulfurized. Its sulfur content is at least 0.5% by weight, preferably at least 1% by weight, more preferably at least 4% by weight, more preferably at least 5% by weight. In addition, the hydrocarbon feedstock treated in the process according to the invention contains asphaltenes. Its asphaltenes content of at least 2% by weight. By "asphaltene" is meant in the present description heavy hydrocarbon compounds insoluble in n-heptane (also called C7 asphaltenes) but soluble in toluene. The quantification of asphaltenes generally uses standard analyzes as defined, for example, in the AFNOR standards T 60-115 (France) or A5TM893-69 (United States). These charges can advantageously be used as they are. Alternatively, they can be diluted by co-charging. This co-charge may be a hydrocarbon fraction or a lighter hydrocarbon fraction mixture, which may preferably be chosen from the products resulting from a fluid catalytic cracking (FCC) process according to the English terminology. Saxon), a light cutting oil (LCO or "light cycle oil" according to the English terminology), a heavy cutting oil (HCO or "heavy cycle oil" according to the English terminology), a decanted oil, a FCC residue, a gas oil fraction, especially a fraction obtained by atmospheric distillation or under vacuum, such as vacuum gas oil, or may come from another refining process. The co-charge may also advantageously be one or more cuts from the liquefaction process of coal or biomass, aromatic extracts, or any other hydrocarbon cuts or non-petroleum fillers such as pyrolysis oil. The heavy hydrocarbon feedstock according to the invention may 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. Hydrotreating Step (a) Said hydrocarbon feedstock is subjected according to the process of the present invention to a fixed bed hydrotreating step (a) in which feedstock and hydrogen are contacted on a hydrotreatment catalyst. . Hydrotreatment, commonly known as HDT, is understood to mean the catalytic treatments with hydrogen supply making it possible to refine, that is to say, to reduce substantially the content of metals, sulfur and other impurities, hydrocarbon feedstocks, while improving the ratio hydrogen on the load and transforming the load more or less partially into lighter cuts. Hydrotreating includes, in particular, hydrodesulfurization reactions (commonly referred to as HDS), hydrodenitrogenation reactions (commonly referred to as HDN), and hydrodemetallation reactions (commonly referred to as HDM), accompanied by hydrogenation, hydrodeoxygenation, hydrogenation, and hydrogenation reactions. hydrodearomatization, hydroisomerization, hydrodealkylation, hydrocracking, hydro-deasphalting and Conradson carbon reduction. According to a preferred variant, the hydrotreatment stage (a) comprises a hydrodemetallation first stage (a1) carried out in one or more hydrodemetallation zones in fixed beds and a second hydrodesulfurization second stage (a2) thereafter. (HDS) carried out in one or more hydrodesulfurization zones in fixed beds. During said first hydrodemetallation step (a1), the feedstock and hydrogen are contacted on a hydrodemetallization catalyst, under hydrodemetallation conditions, and then during said second step (a2). hydrodesulfurization, the effluent of the first step (a1) of hydrodemetallation is brought into contact with a hydrodesulphurization catalyst, under hydrodesulfurization conditions.

This process, known as HYVAHL-FTM, is described, for example, in US Pat. No. 5,417,846. Those skilled in the art readily understand that, in the hydrodemetallization step, hydrodemetallation reactions are carried out but at the same time part of the other hydrotreatment reactions and in particular hydrodesulfurization. Similarly, in the hydrodesulphurization step, hydrodesulphurization reactions are carried out, but also part of the other hydrotreatment reactions and in particular hydrodemetallation reactions. One skilled in the art understands that the hydrodemetallization step begins where the hydrotreatment step begins, where the metal concentration is maximum. Those skilled in the art understand that the hydrodesulfurization step ends where the hydrotreating step ends, where sulfur removal is the most difficult. Between the hydrodemetallation step and the hydrodesulfurization step, the skilled person sometimes defines a transition zone in which all types of hydrotreatment reactions occur. The hydrotreating step (a) according to the invention is carried out under hydrotreatment conditions. It may advantageously be carried out at a temperature of between 300 ° C. and 500 ° C., preferably between 350 ° C. and 420 ° C. and under an absolute pressure of between 2 MPa and 35 MPa, preferably between 11 MPa and 20 ° C. MPa. The temperature is usually adjusted according to the desired level of hydrotreatment and the duration of the targeted treatment. Most often, the space velocity of the hydrocarbon feedstock, commonly referred to as VVH, which is defined as the volumetric flow rate of the feedstock divided by the total catalyst volume, can be in the range of 0.1 to 5 preferably 0.1 to 2, and more preferably 0.1 to 0.45, 11-1. The amount of hydrogen mixed with the feedstock may be between 100 and 5000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feedstock, preferably between 200 Nm3 / m3 and 2000 Nm3 / m3, and more preferably between 300 Nm3 / m3 and 1500 Nm3 / m3. The hydrotreating step (a) can be carried out industrially in one or more liquid downflow reactors.

The hydrotreatment catalysts used are preferably known catalysts. These may be granular catalysts comprising, on a support, at least one metal or metal compound having a hydrodehydrogenating function. These catalysts may advantageously be catalysts comprising at least one Group VIII metal, generally selected from the group consisting of nickel and cobalt, and / or at least one Group VIB metal, preferably molybdenum and / or tungsten. For example, it is possible to use a catalyst comprising from 0.5% to 10% by weight of nickel, preferably from 1% to 5% by weight of nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of nickel. weight of molybdenum, preferably from 5% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO 3) on a mineral support. This support may for example be chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. Advantageously, this support may contain other doping compounds, in particular oxides selected from the group consisting of boron oxide, zirconia, ceria, titanium oxide, phosphoric anhydride and a mixture of these oxides. Most often an alumina support is used and very often a support of alumina doped with phosphorus and possibly boron. When phosphorus pentoxide P205 is present, its concentration is less than 10% by weight. When boron trioxide B205 is present, its concentration is less than 10% by weight. The alumina used may be y (gamma) or hal (eta) alumina. This catalyst is most often in the form of extrudates. The total content of metal oxides of groups VIB and VIII may be from 5% to 40% by weight and in general from 7% to 30% by weight and the weight ratio expressed as metal oxide between metal (or metals) of group VIB on metal (or metals) of group VIII is generally between 20 and 1, and most often between 10 and 2.

In the case of a hydrotreating step including a hydrodemetallation (HDM) step and then a hydrodesulphurization step (HDS), specific catalysts adapted to each step are preferably used. Catalysts which can be used in the HDM step are, for example, indicated in patent documents EP 0113297, EP 0113284, US Pat. No. 5,222,056, US Pat. No. 5,827,421, US Pat. No. 7,110,445, US Pat. No. 5,622,616 and US Pat. No. 5,089,463. HDM catalysts are preferably used. in permutable reactors.

Catalysts that can be used in the HDS step are, for example, indicated in patent documents EP 0113297, EP 0113284, US Pat. No. 6589908, US Pat. No. 4,818,743 or US Pat. No. 6,332,976. A mixed catalyst, active in HDM and HDS, can also be used. both for the HDM section and for the HDS section as described in the patent document FR 2940143. Prior to the injection of the feedstock, the catalysts used in the process according to the present invention are preferably subjected to a sulfurization treatment. in-situ or ex-situ.

According to a preferred embodiment of the present invention, the step (a) of fixed bed hydrotreatment uses a system of permutable reactors, also called guard zones, upstream of the main hydrotreatment reactors. More particularly, the hydrotreating step (a) can be carried out in one or more hydrotreatment zones in fixed beds preceded by at least two hydrotreatment guard zones also in fixed beds, arranged in series to be used in a cyclic manner consisting of the successive repetition of steps a ") and a" ") defined below: a ') a step, in which the guard zones are used together for a duration at most equal to the deactivation time and / or clogging of one of them, a ") a step, during which the deactivated and / or clogged guard zone is short-circuited and the catalyst it contains is regenerated and / or replaced by fresh catalyst, and during which the other guard zone (s) are used, and (a) 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 time of deactivation and / or clogging of one of the guard zones. Preferably, after regeneration and / or replacement of the catalyst of a reactor, this reactor is reconnected downstream of the reactor in operation. The system of reactive reactors is known from patents FR 2681871, FR 2784687 and EP 1343857. The function of the reactive reactors is to protect the main hydrotreating reactors downstream by avoiding clogging and / or deactivation. Indeed, a problem encountered when using fixed beds is the clogging that occurs because of the asphaltenes and sediments contained in the load. Another problem is catalyst deactivation because of the large metal deposition that occurs during hydrotreatment reactions. The switchable reactors are thus used to increase the operating cycle of the hydrotreating unit by allowing the deactivated and / or clogged catalyst to be replaced only in the cyclically operating switchable reactors without stopping the entire unit for a period of time. . The deactivation and / or clogging time varies depending on the feedstock, the operating conditions of the hydrotreating step and the catalyst (s) used. It is generally expressed by a drop in the catalytic performance which can be observed by an increase in the concentration of metals and / or other impurities in the effluent, an increase in the temperature necessary for the maintenance of a catalyst activity or, in the specific case of a clogging, by a significant increase in the pressure drop. The pressure drop 4P, expressing a degree of clogging, can be continuously measured throughout the cycle on each of the zones and can be defined as an increase in pressure resulting from the partially blocked passage of the flow through the zone. Similarly, the temperature can be measured continuously throughout the cycle on each of the two zones.

In order to define a deactivation and / or clogging time, those skilled in the art first define a maximum tolerable value of the pressure drop 4P and / or of the temperature as a function of the charge to be treated, the operating conditions and the conditions. selected catalysts, and from which to proceed with the disconnection of the guard zone. The deactivation and / or clogging time is thus defined as the time when the limit value of the pressure drop and / or the temperature is reached. In the case of a process for the hydrotreatment of heavy fractions, the limit value of the pressure drop is generally between 0.3 MPa and 1 MPa (3 and 10 bar), preferably between 0.5 MPa and 0, 8 MPa (5 and 8 bar). The limit value of the temperature is generally between 400 ° C. and 430 ° C., the temperature corresponding to the measured average temperature of the catalytic bed. The operating conditions of the reactive reactors are generally identical to those of the main hydrotreating reactors. The value of the space velocity VVH of each switchable reactor in operation is preferably between 0.2 h and 4 h -1, more preferably between 1 h -1 to 2 h -1. The overall VVH space velocity value of the permutable reactors and that of each reactor is chosen so as to achieve the maximum hydrodemetallation while controlling the reaction temperature and thus limit the exothermicity. In a preferred embodiment of the invention, there is used a catalyst conditioning section permitting the permutation of these guard zones in operation, that is to say without stopping the operation of the unit. The catalyst conditioning section can comprise the following elements: a system that operates at moderate pressure, preferably between 1 MPa and 5 MPa (10 and 50 bar), and preferably between 1.2 MPa and 2.5 MPa (15 MPa). at 25 bar), which makes it possible to carry out washing, stripping and cooling operations on the disconnected guard reactor before discharging the spent catalyst, then heating and sulphurizing after loading the fresh catalyst; - another system of pressurization / depressurization and gate valves of appropriate technology, which allows to swap these guard zones without stopping the unit since all the operations of washing, stripping, discharging spent catalyst, reloading fresh catalyst, heating and sulphurization are done on the reactor or guard zone disconnected.

Alternatively, a pre-sulphide catalyst can be used in the conditioning section to simplify the permutation procedure while running. The effluent leaving the reactive reactors can then be sent to the main hydrotreating reactors. Each hydrotreatment zone or hydrotreating guard zone may contain at least one catalytic bed, for example 1, 2, 3, 4 or 5 catalytic beds. Preferably, each guard zone contains a catalytic bed. Each catalytic bed may contain at least one catalytic layer containing one or more catalysts, optionally preceded by at least one inert layer, for example alumina or ceramic in the form of extrudates, balls or pellets. The catalysts used in the catalytic bed (s) may be identical or different.

According to a particular embodiment, the hydrocarbon feedstock passes through the inlet of each guard zone a filter plate located upstream of the catalytic bed (s) (s) contained in the guard zone. This filter plate, described for example in patent FR 2889973, advantageously allows to trap the clogging particles contained in the hydrocarbon feedstock by means of a specific distributor plate comprising a filter medium. According to the invention, the effluent from step (a) hydrotreatment in a fixed bed does not undergo any intermediate separation step between the hydrotreatment step (a) and the hydroconversion step (b). This configuration can be described as an integrated schema.

By "without intermediate separation step" is meant in the present invention the fact that at least a portion of the effluent from step (a) hydrotreatment is introduced into the section allowing the implementation of the step (b) bubbling bed hydroconversion without changing chemical composition and without significant pressure loss. The term "separation" means one or more separator tanks and / or one or more stripping columns or distillation, these equipment can operate at different temperatures or pressures. "Significant loss of pressure" means a loss of pressure caused by a valve or expansion turbine, which could be estimated at a pressure loss of more than 10% of the total pressure. Those skilled in the art generally use these pressure losses or relaxations during the separation steps.

In one embodiment of the process according to the invention, all of the effluent from step (a) of hydrotreatment is introduced into the section allowing the implementation of step (b) hydroconversion. In another embodiment, only a portion of the effluent from step (a) hydrotreating is introduced into the section for carrying out step (b) of hydroconversion. This embodiment is however not contradictory to the fact that the method is without an intermediate separation step. This embodiment can consist in dividing the hydrotreatment stage effluent (a) into two streams having the same composition, one going to the hydroconversion stage (b), the other going to a section of separation and fractionating treating hydroconversion effluent (b) downstream thereof. This embodiment can thus be likened to a partial short circuit of the hydroconversion section (b) but, for the part of the effluent of the hydrotreatment section (a) going to the hydroconversion section ( b) bubbling bed, there is no separation, no change in the chemical composition, or significant loss of pressure. Another variant of this short-circuit embodiment may consist in dividing the hydrotreating stage effluent (a) into several streams having the same composition, and sending one or more of these streams to the inlet of a first bubbling bed hydroconversion reactor and one or more of such streams to one or more downstream hydroconversion reactors. Step (b) bubbling bed hydroconversion At least a portion of the effluent from step (a) hydrotreating is sent according to the method of the present invention in a step (b) of hydroconversion which is carried out in at least one reactor containing a catalyst supported in a bubbling bed. Said reactor can operate at an upward flow of liquid and gas. The main purpose of hydroconversion is to convert the heavy hydrocarbon feedstock into lighter cuts while partially refining it.

According to one embodiment of the present invention, a part of the initial hydrocarbon feedstock can be injected directly at the inlet of the hydroconversion section (b) in a bubbling bed, mixed with the effluent of the hydrotreatment section (a). ) in a fixed bed, without this part of the hydrocarbon feed being treated in the hydrotreatment section (a) in a fixed bed. This embodiment can be likened to a partial short circuit of the hydrotreatment section (a) in a fixed bed. According to one variant, a co-charge may be introduced at the inlet of the hydroconversion section (b) in a bubbling bed with the effluent from the hydrotreatment section (a) in a fixed bed. This co-charge can be chosen from atmospheric residues, vacuum residues from direct distillation, deasphalted oils, aromatic extracts from lubricant base production lines, hydrocarbon fractions or a mixture of hydrocarbon fractions that can be chosen. among the products resulting from a fluid-bed catalytic cracking process, in particular a light cutting oil (LCO), a heavy cutting oil (HCO), a decanted oil, or possibly derived from distillation, the gas oil fractions including those obtained by atmospheric or vacuum distillation, such as, for example, vacuum gas oil. According to another variant and in the case where the hydroconversion section has several bubbling bed reactors, this co-charge may be partially or totally injected into one of the reactors downstream of the first reactor. The hydrogen necessary for the hydroconversion reaction may already be present in sufficient quantity in the effluent resulting from the hydrotreatment stage (a) injected at the inlet of the boiling bed hydroconversion section (b). However, it is preferable to provide an additional hydrogen input at the inlet of the hydroconversion section (b). In the case where the hydroconversion section has several bubbling bed reactors, hydrogen can be injected at the inlet of each reactor. The injected hydrogen may be a make-up stream and / or a recycle stream.

Bubbling bed technology is well known to those skilled in the art. Only the main operating conditions will be described here. Bubbling bed technologies conventionally use supported catalysts in the form of extrudates whose diameter is generally of the order of about 1 millimeter, for example 0.9 mm or 1.2 mm. The catalysts remain inside the reactors and are not evacuated with the products, except during the makeup and catalyst withdrawal phases necessary to maintain the catalytic activity. The temperature levels can be high in order to obtain high conversions while minimizing the amounts of catalysts used. The catalytic activity can be kept constant by replacing the catalyst in line. It is therefore not necessary to stop the unit to change the spent catalyst, nor to increase the reaction temperatures along the cycle to compensate for the deactivation. In addition, working at constant operating conditions advantageously provides consistent yields and product qualities along the cycle. Also, because the catalyst is kept agitated by a large recycling of liquid, the pressure drop on the reactor remains low and constant. Because of the attrition of the catalysts in the reactors, the products leaving the reactors may contain fine particles of catalyst. The conditions of the boiling bed hydroconversion stage (b) may be conventional bubbling bed hydroconversion conditions of a liquid hydrocarbon fraction. It can be operated under an absolute pressure of between 2.5 MPa and 35 MPa, preferably between 5 MPa and 25 MPa, more preferably between 6 MPa and 20 MPa, and even more preferably between 11 MPa and 20 MPa at a temperature between 330 ° C and 550 ° C, preferably between 350 ° C and 500 ° C. The space velocity (VVH) and the hydrogen partial pressure are parameters that are set according to the characteristics of the product to be treated and the desired conversion. The VVH (defined as the volumetric flow rate of the feed divided by the total volume of the bubbling bed reactor) is generally in a range from 0.1 h -1 to 10 h -1, preferably 0.2 h -1. 1 to 5 h -1 and more preferably 0.2 h -1 to 1 h -1. The amount of hydrogen mixed with the feedstock is usually from 50 to 5000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feed, most often from 100 Nm3 / m3 to 1500 Nm3 / m3 and preferably 200 Nm3 / m3 at 1200 Nm3 / m3. A conventional hydroconversion granular catalyst comprising, on an amorphous support, at least one metal or metal compound having a hydrodehydrogenating function can be used. This catalyst may be a catalyst comprising Group VIII metals, for example nickel and / or cobalt, most often in combination with at least one Group VIB metal, for example molybdenum and / or tungsten. For example, a catalyst comprising from 0.5% to 10% by weight of nickel and preferably from 1% to 5% by weight of nickel (expressed as nickel oxide NiO) and from 1% to 30% by weight may be used. molybdenum, preferably from 5% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO 3) on an amorphous mineral support. This support may for example be chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. This support may also contain other compounds and for example oxides selected from the group consisting of boron oxide, zirconia, titanium oxide, phosphoric anhydride. Most often an alumina support is used and very often a support of alumina doped with phosphorus and possibly boron. When phosphorus pentoxide P205 is present, its concentration is usually less than 20% by weight and most often less than 10% by weight. When B203 boron trioxide is present, its concentration is usually less than 10% by weight. The alumina used is usually y (gamma) or hal (eta) alumina. This catalyst may be in the form of extrudates. The total content of metal oxides of groups VI and VIII may be between 5% and 40% by weight, preferably between 7% and 30% by weight, and the weight ratio expressed as metal oxide between metal (or metals) of group VI on metal (or metals) of group VIII is between 20 and 1, preferably between 10 and 2. The used catalyst can be partly replaced by fresh catalyst, generally by withdrawal at the bottom of the reactor and introduction at the top of the fresh or new catalyst reactor at regular time interval, that is to say for example by puff or continuously or almost continuously. The catalyst can also be introduced from below and withdrawn from the top of the reactor. For example, fresh catalyst can be introduced every day. The replacement rate of spent catalyst with fresh catalyst may be, for example, from about 0.05 kilograms to about 10 kilograms per cubic meter of charge. This withdrawal and replacement are performed using devices for the continuous operation of this hydroconversion step. The hydroconversion reactor usually comprises a recirculation pump for maintaining the bubbling bed catalyst by continuous recycling of at least a portion of the liquid withdrawn at the top of the reactor and reinjected at the bottom of the reactor. It is also possible to send the spent catalyst withdrawn from the reactor into a regeneration zone in which the carbon and the sulfur contained therein are eliminated before it is reinjected in the hydroconversion stage (b). This hydroconversion step (b) according to the process of the invention can be carried out under the conditions of the H-OIL® process as described, for example, in US Pat. No. 6,270,654. Bubbling bed hydroconversion can be carried out in a single reactor or in several reactors, preferably two, arranged in series. The fact of using at least two bubbling bed reactors in series makes it possible to obtain products of better quality and with better performance. In addition, hydroconversion into two reactors makes it possible to have improved operability in terms of the flexibility of the operating conditions and of the catalytic system. Preferably, the temperature of the second bubbling bed reactor is at least 10 ° C higher than that of the first bubbling bed reactor. The pressure of the second reactor may be 0.1 MPa to 1 MPa lower than for the first reactor to allow the flow of at least a portion of the effluent from the first step without pumping is necessary. The different operating conditions in terms of temperature in the two hydroconversion reactors are selected to be able to control the hydrogenation and the conversion of the feedstock into the desired products in each reactor. In the case where the hydroconversion step (b) is carried out in two substeps (b 1) and (b 2) in two reactors arranged in series, the effluent obtained at the end of the first substep ( b1) may optionally be subjected to a separation step of the light fraction and the heavy fraction, and at least a portion, preferably all, of said heavy fraction may be treated in the second substep (b2) of hydroconversion. This separation is advantageously done in an inter-stage separator, as described for example in US Pat. No. 6,270,654, and in particular makes it possible to avoid over cracking of the light fraction in the second hydroconversion reactor. It is also possible to transfer all or part of the used catalyst withdrawn from the reactor of the first sub-stage (b1) of hydroconversion, operating at a lower temperature, directly to the reactor of the second substep (b2), operating at higher temperature, or to transfer all or part of the used catalyst withdrawn from the reactor of the second substep (b2) directly to the reactor of the first substep (b 1). This cascade system is for example described in US Pat. No. 4,816,841. Step (c) of separation of the hydroconversion effluent The method according to the invention furthermore comprises a step (c) of separation which makes it possible to obtain from at least one gaseous fraction and at least one liquid hydrocarbon fraction. The effluent obtained at the end of the hydroconversion stage (b) comprises a liquid fraction and a gaseous fraction containing the gases, in particular H 2, H 2 O, NEI 3, and C 1 -C 4 hydrocarbons. This gaseous fraction can be separated from the hydrocarbon effluent by means of separating devices well known to those skilled in the art, in particular by means of one or more separator flasks that can operate at different pressures and temperatures, possibly associated with each other. to a means of stripping with steam or hydrogen. The effluent obtained at the end of the hydroconversion stage (b) is advantageously separated in at least one separator flask into at least one gaseous fraction and at least one liquid fraction. These separators may for example be high temperature high pressure separators (HPHT) and / or high temperature low pressure separators (HPBT). After possible cooling, this gaseous fraction is preferably treated in a hydrogen purification means so as to recover the hydrogen that is not consumed during the hydrotreatment and hydroconversion reactions. The hydrogen purification means may be an amine wash, a membrane, a PSA (Pressure Swing Adsorption) system, or several of these means arranged in series. The purified hydrogen can then advantageously be recycled in the process according to the invention, after possible recompression. The hydrogen may be introduced at the inlet of the hydrotreatment step (a) and / or at different locations during the hydrotreatment stage (a) and / or at the inlet of the stage (b). hydroconversion and / or at different locations during step (b) hydroconversion.

The separation step (c) may also comprise atmospheric distillation and / or vacuum distillation. Advantageously, the separation step (c) further comprises at least one atmospheric distillation, in which the liquid hydrocarbon fraction (s) obtained (s) after separation is (are) fractionated (s) by atmospheric distillation into at least one atmospheric distillate fraction and at least one atmospheric residue fraction. The atmospheric distillate fraction may contain commercially recoverable fuels bases (naphtha, kerosene and / or diesel), for example in the refinery for the production of motor and aviation fuels. In addition, the separation step (c) of the process according to the invention may advantageously also comprise at least one vacuum distillation in which the liquid hydrocarbon fraction (s) obtained (s) after separation and / or the atmospheric residue fraction obtained after atmospheric distillation is (are) fractionated by vacuum distillation into at least one vacuum distillate fraction and at least one vacuum residue fraction. Preferably, the separation step (c) firstly comprises an atmospheric distillation, in which the liquid hydrocarbon fraction (s) obtained (s) obtained after separation is (are) fractionated ( s) by atmospheric distillation into at least one atmospheric distillate fraction and at least one atmospheric residue fraction, followed by vacuum distillation in which the atmospheric residue fraction obtained after atmospheric distillation is fractionated by vacuum distillation into at least one vacuum distillate fraction and at least one residue fraction under vacuum. The vacuum distillate fraction typically contains vacuum gas oil fractions. At least a portion of the vacuum residue fraction can be recycled to the hydroconversion stage (b). At the end of the separation step (c), at least one liquid hydrocarbon fraction having a sulfur content of less than or equal to 0.5% by weight, preferably less than or equal to 0.3% by weight, can be obtained. more preferably less than or equal to 0.1% by weight, and even more preferably less than or equal to 0.08% by weight. This liquid hydrocarbon fraction may advantageously serve as a fuel oil base, especially for a bunker oil. Advantageously, all of the liquid hydrocarbon effluent obtained at the end of the separation step (c) may have a sulfur content of less than or equal to 0.5% by weight, preferably less than or equal to 0.3%. by weight, more preferably less than or equal to 0.1% by weight, and even more preferably less than or equal to 0.08% by weight. In the context of the present invention, the conversion of the hydrocarbon feedstock into lighter fractions may be between 10% and 95%, preferably between 25% and 90%, and more preferably between 40% and 85%. The conversion rate mentioned above is defined as the amount of compounds having a boiling point above 520 ° C in the initial hydrocarbon feedstock, minus the amount of compounds having a boiling point above 520 ° C in the hydrocarbon effluent obtained at the end of the hydroconversion stage (b), all divided by the amount of compounds having a boiling point greater than 520 ° C. in the initial hydrocarbon feedstock. A high conversion rate is advantageous insofar as this conversion rate illustrates the production of conversion products, mainly atmospheric distillates and / or vacuum distillates of the naphtha, kerosene and diesel type, in a significant amount. This liquid hydrocarbon effluent may, at least in part, advantageously be used as fuel oil bases or as fuel oil, especially as a base of bunker oil or as fuel oil, with low sulfur content meeting the new recommendations of the International Maritime Organization . By "fuel" is meant in the invention a hydrocarbon feedstock used as fuel. By "oil base" is meant in the invention a hydrocarbon feed which, mixed with other bases, constitutes a fuel oil. Depending on the origin of these bases, in particular depending on the type of crude oil and the type of refining, the properties of these bases, in particular their sulfur content and their viscosity, are very diverse. Optional step (d) for separation of sediments and fines The hydrocarbon effluent obtained at the end of hydroconversion stage (b), and in particular the heavier liquid fraction obtained, may contain sediments and residues of catalyst from the fixed stage and / or the bubbling bed stage in the form of fines. In order to obtain a fuel oil or a fuel base that meets the recommendations for a sediment content after aging of less than or equal to 0.1%, the process according to the invention may comprise an additional step of separating the sediments and the fines. the liquid hydrocarbon effluent after the separation step (c). The method according to the invention may therefore further comprise a step (d) for separating sediments and fines, in which at least a portion of the atmospheric residue and / or vacuum distillate and / or vacuum residue fractions are subjected to separation of sediments and catalyst fines, using at least one filter, centrifuge system or inline decantation.

Optional Step (e) of Catalytic Cracking According to one embodiment, the method according to the invention may further comprise a catalytic cracking step (e), wherein at least a part of the vacuum distillate fraction and / or the fraction vacuum residue, optionally previously subjected to the step of separation of sediments and fines (d), is sent to a catalytic cracking section in which it is treated under conditions allowing the production of a gaseous fraction, a fraction gasoline, a diesel fraction and a residual fraction. Said step (e) of catalytic cracking may be a catalytic cracking step in a fluidized bed, for example according to the process developed by the Applicant Company called R2R. This step can be carried out in a conventional manner known to those skilled in the art under the appropriate cracking conditions in order to produce lower molecular weight hydrocarbon products. Functional descriptions and catalysts that can be used for fluidized bed cracking in this step (e) are described, for example, in US Pat. No. 4,695,370, EP 0184517, US Pat. No. 4,959,334, EP 0323297, US Pat. No. 4,365,232 and US Pat. 5344554, US 5449496, EP 0485259, US 5286690, US 5324696, EP 0542604 and EP 0699224. The fluidized catalytic cracking reactor can operate upward or downward. Although this is not a preferred embodiment of the present invention, it is also conceivable to perform catalytic cracking in a moving bed reactor. Particularly preferred catalytic cracking catalysts are those containing at least one zeolite usually in admixture with a suitable matrix such as, for example, alumina, silica, silica-alumina. At least a portion of the residual fraction obtained at the end of the catalytic cracking step (e), often referred to as "slurry" fraction by a person skilled in the art, may be recycled at the inlet of step (e). ) of catalytic cracking and / or at the inlet of the hydrotreatment step (a) and / or at the entry of the hydroconversion stage (b). The residual fraction may also be at least partly or even entirely sent to a refinery heavy fuel oil storage zone. In one embodiment of the invention, a portion of the diesel fraction and / or the residual fraction obtained at the end of this catalytic cracking step (e) may be used to form a fluxing base. Fluxing and Fuel Oil One objective of the present invention is to produce marketable fuel oils, especially bunker fuels for maritime transport. It is preferable that this type of fuel meets certain specifications, especially in terms of viscosity. Preferably, a very common type of bunker oil has a viscosity of less than or equal to 380 cSt (at 50 ° C). Other qualities of fuel oil, called "grades", meet different specifications, especially from the point of view of viscosity. Particularly for distillate type fuels, the DMA grade imposes a viscosity of between 2 cSt and 6 cSt at 40 ° C. and the DMB grade has a viscosity of between 2 cSt and 11 cSt at 40 ° C. In order to obtain, among other things, the target viscosity of the desired fuel grade, oil bases may be mixed, if necessary, with fluxing bases or "cutter stocks" according to the English terminology. Fuel specifications are for example described in the IS08217 standard (last version in 2012). The fluxing bases are generally of the kerosene, diesel or vacuum gas oil type. They can be chosen from oils of light cutting oils (LCO) of a catalytic cracking, heavy cutting oils (HCO) of a catalytic cracking, the residue of a catalytic cracking, kerosene, diesel fuel, vacuum distillate and / or decanted oil.

In the process according to the invention, the atmospheric residue and / or the vacuum distillate and / or the vacuum residue obtained (s) at the end of the separation step (c), possibly previously subjected to the step (d) separating sediments and fines, may be mixed with one or more fluxing bases selected from the group consisting of light catalytic cracking oils, heavy-duty cutting oils, and catalytic cracking, the residue of a catalytic cracking, a kerosene, a gas oil, a vacuum distillate and / or a decanted oil. In a very particularly preferred manner, said fluxing base is chosen from a part of the diesel fraction and / or of the residual fraction obtained at the end of the catalytic cracking step (e). In addition or alternatively, said fluxing base may be chosen from a part of the kerosene and / or diesel fraction obtained at the end of the boiling bed hydroconversion stage. At the end of this step of mixing the atmospheric residue and / or the vacuum distillate and / or the vacuum residue obtained (s) at the end of the separation step (c), possibly previously subjected to Step (d) of separation of sediments and fines, with one or more fluxing bases, advantageously obtained a fuel oil used in shipping, also called bunker oil, low sulfur content. The present invention therefore also relates to such a fuel oil having a sulfur content of less than or equal to 0.5% by weight, preferably less than or equal to 0.1% by weight. This oil can advantageously have a sediment content of less than or equal to 0.1% by weight, so as to comply with the new version of the ISO 8217: 2012 standard. In addition, the viscosity of this oil may be between 1 cSt and 700 cSt at 50 ° C. An advantageous embodiment of the method according to the invention is shown in FIGS. 1 and 2. FIG. 1 represents a method according to the invention in an integrated diagram, that is to say without intermediate separation and without significant decompression between the fixed bed section and the bubbling bed section. For more legibility, the operation of the guard zones in the hydrotreatment section of FIG. 1 is described in FIG.

In FIG. 1, the charge (10), preheated in the enclosure (12), mixed with recycled hydrogen (64) and additional hydrogen (24) preheated in the enclosure (16), via the common line (14) for the makeup hydrogen mixture and the recycled hydrogen is introduced via the line (18) into the guard zone system.

Referring to FIG. 2, the operation of the guard zones in the hydrotreatment section comprising two guard zones (or reactive reactors) Ra and Rb comprises a series of cycles each comprising four successive stages: a first step (step i) during which the charge successively passes through the reactor Ra, then the reactor Rb, - a second step (step ii) during which the charge passes only through the reactor Rb, the reactor Ra being short-circuited for regeneration and / or replacement of the catalyst, a third step (step iii) during which the charge successively passes through the reactor Rb, then the reactor Ra, a fourth step (step iv) during which the feed passes only through the reactor Ra, the reactor Rb being short-circuited for regeneration and / or replacement of the catalyst. The cycle can then start again. Steps i and iii are steps during which all guard zones are used.

Steps ii and iv are steps during which one guard area is short-circuited while the other is used. During step (i), the preheated charge is introduced via the line (18) and the line (19) comprising a valve V1 open towards the line (20) and the guard reactor Ra containing a fixed bed A of catalyst. During this period valves V3, V4 and V5 are closed.

The effluent from the reactor Ra is sent via the pipe (21), the pipe (22) comprising an open valve V2 and the pipe (23) into the guard reactor Rb containing a fixed bed B of catalyst. The effluent from the reactor Rb is sent through the lines (24) and (25) comprising an open valve V6 and the pipe (26) to the main hydrotreatment section which will be described later.

During step (ii), the valves V1, V2, V4 and V5 are closed and the charge is introduced via the line (18) and the line (27) comprising a valve V3 open towards the line (23) and the reactor Rb. During this period, the effluent from the reactor Rb is sent through the lines (24) and (25) having an open valve V6 and the pipe (26) to the main hydrotreatment section. During step (iii), the valves V1, V2 and V6 are closed and the valves V3, V4 and V5 are open. The charge is introduced via the line (18) and the lines (27) and (23) to the reactor Rb. The effluent from the reactor Rb is sent via the pipe (24), the pipe (28) having an open valve V4 and the pipe (20) into the guard reactor Ra.

The effluent from the reactor Ra is sent through the lines (21) and (29) having an open valve V5 and the pipe (26) to the main hydrotreatment section. During step (iv), the valves V2, V3, V4 and V6 are closed and the valves V1 and V5 are open. The charge is introduced via line (18) and lines (19) and (20) to the reactor Ra. During this period, the effluent from the reactor Ra is sent through the lines (21) and (29) comprising an open valve V5 and the pipe (26) to the main hydrotreatment section. Returning to FIG. 1, the effluent leaving the at least one holding reactor is optionally remixed with hydrogen arriving via line (65) in an HDM reactor (30) which contains a fixed bed (32) of catalyst . For clarity, a single HDM reactor and a single HDS reactor are shown in the figure, but the HDM and HDS section may have multiple HDM and HDS reactors in series. If necessary, the recycled and / or auxiliary hydrogen can also be introduced into the hydrotreatment reactors between the different catalytic beds (not shown). The effluent from the HDM reactor is withdrawn through line (34) and sent to the first HDS reactor (36) where it passes through a fixed bed (38) of catalyst. The effluent from the hydrotreatment stage is sent via line (42) to the bubbling bed hydroconversion section via an optional heat exchanger (43). The effluent from the hydrotreating step going to the bubbling bed hydroconversion section may optionally be mixed with a co-charge (94) and / or optionally mixed with recycled hydrogen (88) optionally supplemented with makeup hydrogen (90) preheated in the furnace (91). The effluent from the hydrotreatment stage or the mixture constituted with a co-charge and / or hydrogen is then introduced via the line (96) in the hydroconversion stage at the bottom of the first reactor (98) bubbling bed operating at upward flow of liquid and gas and containing at least one hydroconversion catalyst. The reactor (98) usually comprises a recirculation pump (100) for maintaining the bubbling bed catalyst by continuously recycling at least a portion of the liquid withdrawn into the upper part of the reactor and reinjected at the bottom of the reactor. The addition of fresh catalyst can be done from the top or the bottom of the reactor (not shown). The catalyst supply can be carried out periodically or continuously. The spent catalyst can be withdrawn from the bottom of the reactor (not shown) to either be removed or regenerated to remove carbon and sulfur prior to reinjection from the top of the reactor. The catalyst withdrawn from the bottom of the first partially used reactor can also be transferred directly to the top of the second hydroconversion reactor (102) (not shown). Optionally, the converted effluent (104) from the reactor (98) may be separated from the light fraction (106) in an inter-stage separator (108). All or part of the effluent (110) from the inter-stage separator (108) is advantageously mixed with additional hydrogen (157), if necessary preheated (not shown). This mixture is then injected via the pipe (112) into a second bubbling bed hydroconversion reactor (102) operating with an upward flow of liquid and gas containing at least one hydroconversion catalyst. The operating conditions, in particular the temperature, in this reactor are chosen to reach the desired conversion level, as previously described. Addition and removal of the catalyst is carried out in the same manner as described for the first reactor. The reactor (102) also usually includes a recirculation pump (114) operating in the same manner as the pump of the first reactor. The effluent from bubbling bed reactors is sent via line (134) to a high temperature high pressure (HPHT) separator (136) from which a gaseous fraction (138) and a liquid fraction (140) are recovered. The gaseous fraction (138) is sent generally via an exchanger (not shown) or a dry cooler (142) for cooling to a low temperature high pressure separator (HPBT) (144) from which a gaseous fraction (146) containing the gaseous fraction (146) is recovered. gas (H2, H2S, NE13, C1-C4 hydrocarbons ...) and a liquid fraction (148).

The gaseous fraction (146) of the low temperature high pressure separator (HPBT) (144) is treated in the hydrogen purification unit (150) from which hydrogen (152) is recovered for recycling via the compressor. (154) and line (156) and / or line (157) to the hydroconversion section. The hydrogen purification unit may consist of an amine wash, a membrane, a PSA type system. The gases containing undesirable nitrogen and sulfur compounds are removed from the installation (stream (158) which may represent several streams, in particular a flow rich in H2S and one or more purges containing light hydrocarbons (Cl and C2) which can (can ) be used in refinery fuel gas).

The liquid fraction (148) of the low temperature high pressure separator (HPBT) (144) is expanded in the device (160) and sent to the fractionation system (172). Optionally, a medium pressure separator (not shown) after the expander (160) can be installed to recover a vapor phase that is sent to the purification unit (150) and / or a dedicated medium pressure purification unit (not shown). ), and a liquid phase which is fed to the fractionation section (172). The liquid fraction (140) from the high temperature high pressure separation (HPHT) (136) is expanded in the device (174) and sent to the fractionation system (172). Optionally, a medium pressure separator (not shown) after the expander (174) can be installed to recover a vapor phase that is sent to the purification unit (150) and / or to a dedicated medium pressure purification unit (not shown). ), and a liquid phase which is fed to the fractionation section (172). Of course, the fractions (148) and (140) can be sent together, after expansion, to the system (172). The fractionation system (172) comprises an atmospheric distillation system for producing a gaseous effluent (176), at least a so-called light fraction (178), containing in particular naphtha, kerosene and diesel, and an atmospheric residue fraction (180). ). Part of the atmospheric residue fraction (180) can be withdrawn via line (182) to form the desired oil bases. All or part of the atmospheric residue fraction (180) can be sent to a vacuum distillation column (184) to recover a fraction containing the vacuum residue (186) and a vacuum distillate fraction (188) containing vacuum gas oil . At least a portion of the vacuum residue fraction is preferably recycled via line (190) to the hydroconversion stage, or upstream of the hydrotreating step (line not shown) to increase the conversion. Optionally, the atmospheric residue fraction (182), the vacuum distillate fraction (188) and / or the vacuum residue fraction (186) can be subjected to a fines and sediment separation step by, for example, filters (191). ), (192) and (193) respectively.

An alternative scheme not shown for separation and fractionation can be achieved by means of a steam stripping column which processes the heavy fraction (s) of the high pressure or medium pressure or low pressure separators. By this means, the bottom of the stripping column directly feeds the vacuum column; the atmospheric distillation column remains to process distillate mixtures but does not treat the unconverted (heavier) fraction. EXAMPLES Example The following example illustrates the invention without however limiting its scope.

A vacuum residue (RSV Arabian Heavy) containing 88.6% by weight of compounds boiling at a temperature above 520 ° C, having a density of 6.2 ° API and a sulfur content of 5.2% was treated in mass. The feedstock was subjected to a hydrotreatment step including two permutable reactors. The operating conditions of the step in fixed bed (s) are given in Table 1. HDM and HDS NiMo catalysts on Alumina T (° C) 380 Pressure, MPa 15 VVH (h-1, Sm3 / h charge fresh / m3 of fixed bed catalyst) 0.12 H2 / HC fixed bed section input excluding H2 consumption (NM3 / m3 fresh feed) 1000 Table 1: Fixed bed operating conditions The effluent from the hydrotreating was not subjected no separation and is sent directly in a hydroconversion stage comprising two successive bubbling bed reactors. The operating conditions of the boiling bed stage (s) are given in Table 2. NiMo catalyst on Alumina T bubbling bed R1 (° C) 420 T bubbling bed R2 (° C) 430 pressure, MPa 14, 5 VVH (11-1, Sm3 / h fresh load / m3 boiling bed reactors) 0.3 H2 / HC inlet boiling bed section excluding H2 consumption (\ IM3 / m3 fresh feed) 1000 Table 2: Operating conditions bubbling bed The yield and the sulfur content of each fraction obtained from the effluent leaving the hydroconversion section are given in Table 3. Yield Yield (% wt) S (% wt) NH3 0.5 0 H2S 5.3 94, 12 Cl-C4 (gas) 5.60 Naphtha (PI - 150 ° C) 10.2 0.003 Diesel (150 ° C - 350 ° C) 28.2 0.02 Vacuum distillate (350 ° C - 520 ° C) ) 28.3 0.11 Vacuum Residue (520 ° C +) 25.2 0.67 Table 3: Yields and Sulfur Content of Bubble Bed Effluent (% w / fresh charge) Hydrogen consumed represents 3.4% by weight of the fresh feed introduced e at the inlet of the hydrotreatment section. The above yields make it possible to calculate the conversion rate of the fraction of the filler boiling at a temperature above 520 ° C converted into products boiling at a temperature below 520 ° C, according to the following formula: - - L Numerical application gives: Conversion = (88.6-25.2) / 88.6 = 71.5% This particularly high conversion rate illustrates the production of conversion products (mainly distillates) in a significant amount.

Subsequently, a mixture was prepared from 350-520 ° C and 520 ° C + cuts from the hydroconversion stage in the following proportions: - cut 350-520 ° C: 44% by weight of the mixture and 520 ° C + cut: 56% by weight of the mixture. There was thus obtained a fuel oil having a sulfur content of 0.42% by weight and having a viscosity of 380 cSt at 50 ° C. In addition, its sediment content after aging is less than 0.1% by weight. In view of these analyzes, this fuel oil is particularly suitable to form a fuel oil as recommended by the IMO outside the ZCESs by 2020-2025.

A second mixture consisting of 20% by weight of a fraction obtained from the diesel cut and 80% by weight of a fraction obtained from the vacuum distillate cut was also produced. In these proportions, the mixture has a sulfur content of 0.09% and a viscosity of 6 cSt at 40 ° C. This mixture thus constitutes a marine fuel of the distillate type ("marine diesel" or "marine diesel" in the English terminology) which can be likened to the DMB grade (whose viscosity specification is between 2 cSt and 11 cSt at 40.degree. ° C) for example. Because of its sulfur content of less than 0.1%, this mixture is a fuel of choice for ZCESs by 2015.

Claims (16)

REVENDICATIONS1. Process for treating a hydrocarbon feed having a sulfur content of at least 0.5% by weight, an asphaltene content of at least 2% by weight, an initial boiling point of at least 340 ° C and a final boiling temperature of at least 440 ° C, to obtain at least one liquid hydrocarbon fraction having a sulfur content of less than or equal to 0.5% by weight, comprising the following successive steps: a) a fixed bed hydrotreatment step, in which the hydrocarbon feedstock and hydrogen are contacted on at least one hydrotreatment catalyst, b) a step of hydroconversion of at least a portion of the effluent from step (a) in at least one reactor containing a catalyst supported in bubbling bed, and c) a step of separating the effluent from step (b) to obtain at least one gaseous fraction and at least said fraction hydrocarbon liquid, without intermediate separation step in the hydrotreatment step (a) and the hydroconversion step (b). 2. The method of claim 1 wherein the step (a) of hydrotreating comprises a first step (a1) hydrodemetallation (HDM) carried out in one or more hydrodemetallation zones in fixed beds and a second step (a2). subsequent hydrodesulfurization (HDS) carried out in one or more fixed bed hydrodesulfurization zones. 3. Method according to either of claims 1 and 2, wherein the hydrotreating step (a) is carried out at a temperature between 300 ° C and 500 ° C, under an absolute pressure between 2 MPa and 35 MPa, with a space velocity of the hydrocarbon feedstock in a range of 0.1 hr-1 to 5 hr-1, and the amount of hydrogen blended with the feed is between 100 Nm3 / m3 and 5000 Nm3 / m3. 4. Process according to any one of Claims 1 to 3, in which the hydroconversion step (b) is carried out under an absolute pressure of between 2.5 MPa and 35 MPa, at a temperature of between 330 ° C. and 550 ° C, with a space velocity in the range of 0.1 111 to 10 111, and the amount of hydrogen mixed with the feed is 50 Nm3 / m3 to 5000 Nm3 / m3. 5. Method according to any one of claims 1 to 4, wherein the step (a) of hydrotreating is carried out in one or more hydrotreating zones in fixed beds preceded by at least two guard zones. hydrotreatment also in fixed beds, arranged in series for cyclic use consisting of the successive repetition of steps a ") and a") defined hereinafter: a ') a step, in which the guard zones are used all together for a time at most equal to the time of deactivation and / or clogging of one of them, a ") a step, during which the guard zone deactivated and / or clogged is short-circuited and the catalyst qu it contains is regenerated and / or replaced by fresh catalyst, and during which the other guard zone (s) are used, and (a) 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 period at most equal to the time of deactivation and / or clogging of one of the guard zones. 6. Method according to any one of claims 1 to 5, wherein the hydrocarbon feedstock is selected from atmospheric residues, vacuum residues from direct distillation, crude oils, crude oils topped, deasphalting resins, asphalts or deasphalting pitches, residues resulting from conversion processes, aromatic extracts from lubricant base production lines, oil sands or derivatives thereof, oil shales or their derivatives, source rock oils or their derivatives, taken alone or mixed. The process according to any one of claims 1 to 6, wherein the separation step (c) further comprises at least one atmospheric distillation, wherein the hydrocarbon fraction (s) is (are) liquid (s) obtained after separation is (are) fractionated by atmospheric distillation into at least one atmospheric distillate fraction and at least one atmospheric residue fraction. The process according to any one of claims 1 to 7, wherein the separation step (c) further comprises at least one vacuum distillation in which the hydrocarbon fraction (s) is (are) liquid (s) obtained after separation and / or the atmospheric residue fraction obtained after atmospheric distillation is (are) fractionated by vacuum distillation into at least one vacuum distillate fraction and at least one vacuum residue fraction. The process of claim 8, wherein at least a portion of the vacuum residue fraction is recycled to the hydroconversion step (b). 10 The method of any of claims 7 to 9, further comprising a step (d) of separating sediments and fines, wherein at least a portion of the atmospheric residue and / or distillate fractions under vacuum and / or residue Under vacuum, sediment and catalyst fines are separated using at least one filter, centrifuge system or in-line decantation. 11. Process according to any one of claims 8 to 10, further comprising a catalytic cracking step (e), in which at least a portion of the vacuum distillate fraction and / or the vacuum residue fraction, optionally beforehand. subjected to the sediment and fines separation step (d), is sent to a catalytic cracking section in which it is treated under conditions allowing the production of a gaseous fraction, a gasoline fraction, a diesel fraction and a residual fraction. 25 12. Process according to any one of claims 7 to 11, in which the atmospheric residue and / or the vacuum distillate and / or the vacuum residue obtained at the end of the separation step (c). , optionally previously subjected to step (d) for separating sediments and fines, is (are) mixed with one or more fluxing bases selected from the group consisting of light cutting oils of a catalytic cracking, Catalytically cracked heavy cutting oils, catalytic cracking residue, kerosene, gas oil, vacuum distillate and / or decanted oil. 13. The method of claim 12, wherein said fluxing base is selected from a portion of the diesel fraction and / or the residual fraction obtained at the end of the catalytic cracking step (e). 14. Fuel oil usable in maritime transport, obtained by the process as defined in either of claims 12 or 13, having a sulfur content of less than or equal to 0.5% by weight, preferably less than or equal to 0.1% by weight. 15. Fuel oil according to claim 14, characterized in that it has a sediment content less than or equal to 0.1% by weight. 16. Fuel oil according to either of claims 14 or 15, characterized in that its viscosity is between 1 cSt and 700 cSt at 50 ° C.