EP3018189A1 - Process for converting petroleum feedstocks comprising a visbreaking stage, a maturation stage and a stage of separating the sediments for the production of fuel oils with a low sediment content - Google Patents

Abstract

The invention relates to a process for converting a hydrocarbon feedstock containing at least one hydrocarbon fraction having a sulfur content of at least 0.1% by weight, an initial boiling point of at least 340.degree. a final boiling temperature of at least 440 ° C to obtain a heavy fraction having a sediment content after aging less than or equal to 0.1% by weight, said process comprising the following steps: a) a step of visbreaking of the feedstock in at least one maturation chamber, b) a step of separating the effluent obtained at the end of step a), c) a step of maturation of the heavy fraction resulting from step b d) a step of separating the sediments from the heavy fraction resulting from the curing step c) to obtain said fraction.

Description

The present invention relates to the refining and the conversion of heavy hydrocarbon fractions containing, inter alia, sulfur-containing impurities. It relates more particularly to a process for converting heavy petroleum feeds of the atmospheric residue type and / or vacuum residue for the production of heavy fractions that can be used as fuel bases, in particular bunker oil bases, with a low sediment content. The process according to the invention also makes it possible to produce atmospheric distillates (naphtha, kerosene and diesel), vacuum distillates and light gases (C1 to C4).

The quality requirements for marine fuels are described in ISO 8217. The sulfur specification now focuses on SO _x emissions (Annex VI of the MARPOL Convention of the International Maritime Organization) and results in a recommendation for sulfur content not exceeding 0.5% by weight outside the Sulfur Emission Control Areas (ZCES or Emissions Control Areas / ECA) by 2020-2025 and less than or equal to 0,1% in ZCES. Another very restrictive recommendation is the sediment content after aging according to ISO 10307-2 (also known as IP390) which must be less than or equal to 0.1%.

The sediment content according to ISO 10307-1 (also known as IP375) is different from the sediment content after aging according to ISO 10307-2 (also known as IP390). The sediment content after aging according to ISO 10307-2 is a much more stringent specification and corresponds to the specification for bunker fuels.

According to Annex VI of the MARPOL Convention, a ship may therefore use a sulfur-containing fuel oil if the ship is equipped with a flue gas treatment system that reduces emissions of sulfur oxides.

Residue visbreaking processes are used to convert low value residues to higher value added distillates. The visbreaking consists of partially cracking the residue, the conversion is therefore always significantly lower (by at least 10 to 20%) than that obtained in a hydrocracking process. ebullated bed residue for example. However, the resulting heavy fraction corresponding to the unconverted residual cut is generally unstable. It contains sediments that are mainly precipitated asphaltenes. This unstable residual cut can not therefore be used as fuel, especially in bunker oil without a specific treatment since the visbreaking is operated under severe conditions leading to a high conversion rate for this type of treatment. However, the implementation of a visbreaking process is much less expensive than a process for hydrocracking residues. In addition, a large number of units is already installed, so there is interest in using these units while allowing them to improve the quality of the effluents and thus allow them to operate with greater severity.

The visbreaking process partially converts heavy feeds to produce atmospheric distillates and / or vacuum distillates. Residual type feeds generally contain asphaltenes which can precipitate during visbreaking. Initially in the feedstock, the visbreaking conditions and in particular the temperature cause the asphaltenes to undergo reactions (dealkylation, polymerization, etc.) leading to their precipitation when the conditions are severe and the conversion rate is high for this type. process. In comparison with a residue hydrocracking process, the use of a visbreaking process in the absence of hydrogen and of catalyst makes the reactions only thermal. Thus the conversion rate at which sediments appear visbreduction is lower than in hydrocracking of residues. The sediments formed must be removed to satisfy a product quality such as bunker oil. Such separation of the sediments avoids in particular the risk of clogging of the boat engines and in the case of any processing steps implemented downstream of the visbreaking step, to avoid clogging of the bed (s) catalytic (s) implemented.

The applicant in his research has developed a new process incorporating a stage of maturation and separation of sediments downstream of a visbreaking stage. It has been found that such a process makes it possible to obtain fractions heavy having a low sediment content after aging, said heavy fractions may advantageously be used in whole or in part as fuel oil or as fuel oil base meeting the future specifications, namely a sediment content after aging less than or equal to 0.1% in weight

1. a) une étape de viscoréduction de la charge dans au moins une chambre de maturation,
2. b) une étape de séparation de l'effluent obtenu à l'issue de l'étape a) en au moins une fraction légère d'hydrocarbures contenant des bases carburants et une fraction lourde contenant des composés bouillant à au moins 350°C,
3. c) une étape de maturation de la fraction lourde issue de l'étape b) de séparation permettant la transformation d'une partie des sédiments potentiels en sédiments existants, réalisée pendant une durée comprise entre 1 et 1500 minutes, à une température comprise entre 50 et 350°C, et une pression inférieure à 20 MPa,
4. d) une étape de séparation des sédiments de la fraction lourde issue de l'étape c) de maturation pour obtenir ladite fraction lourde.

More particularly, the invention relates to a process for converting a hydrocarbon feedstock containing at least one hydrocarbon fraction having a sulfur content of at least 0.1% by weight, an initial boiling temperature of at least 340 ° C and a final boiling temperature of at least 440 ° C to obtain a heavy fraction having a sediment content after aging less than or equal to 0.1% by weight, said process comprising the following steps:

1. a) a visbreaking step of the charge in at least one maturation chamber,
2. b) a step of separating the effluent obtained at the end of step a) into at least a light hydrocarbon fraction containing fuels bases and a heavy fraction containing compounds boiling at least 350 ° C,
3. c) a step of maturation of the heavy fraction resulting from the separation stage b) allowing the transformation of a part of the potential sediments into existing sediments, carried out for a period of between 1 and 1500 minutes, at a temperature of between 50 and and 350 ° C, and a pressure of less than 20 MPa,
4. d) a step of separating the sediments from the heavy fraction resulting from the curing step c) to obtain said heavy fraction.

In order to form the fuel oil in accordance with the viscosity recommendations, the heavy fractions obtained by the present process can be mixed with fluxing bases so as to achieve the target viscosity of the desired fuel grade.

Another point of interest of the process is the partial conversion of the feedstock to produce, especially by visbreaking, atmospheric distillates or vacuum distillates (naphtha, kerosene, diesel, vacuum distillate), recoverable as bases in the fuel pools. directly or after passing through a other refining process such as hydrotreating, reforming, isomerization-hydrocracking or catalytic cracking.

detailed description Load

The feedstocks treated in the process according to the invention are advantageously chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, crude head oils, deasphalted oils, deasphalting resins, asphalts or pitches. deasphalting, residues resulting from conversion processes, aromatic extracts from lubricant base production lines, oil sands or their derivatives, oil shales or their derivatives, whether alone or as a mixture.

These fillers can advantageously be used as they are or else diluted by a hydrocarbon fraction or a mixture of hydrocarbon fractions which may be chosen from products resulting from a fluid catalytic cracking process (FCC according to the initials of the English name of "Fluid Catalytic Cracking"), a light cutting oil (LCO), a heavy cutting oil (HCO), a decanted oil (OD according to the initials of the English name "Decanted Oil"), a residue of FCC , or which may come from the distillation, gas oil fractions including those obtained by atmospheric or vacuum distillation, such as vacuum gas oil. The heavy charges can also advantageously comprise 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 fillers according to the invention generally have a sulfur content of at least 0.1% by weight, an initial boiling point of at least 340 ° C. and a final boiling point of at least 440 ° C. preferably a final boiling temperature of at least 540 ° C. Advantageously, the load can contain at least 1% C7 asphaltenes and at least 5 ppm metals, preferably at least 2% C7 asphaltenes and at least 25 ppm metals.

The fillers according to the invention are preferably atmospheric residues or residues under vacuum, or mixtures of these residues.

Step a) : Viscoreduction

The filler according to the invention is subjected to a visbreaking stage in at least one maturation chamber.

This step consists in partially cracking the filler in order to reduce its viscosity.

The visbreaking step (visbreaking according to the English terminology) is a mild cracking process in which heavy hydrocarbons are heated in a maturation chamber (soaker according to the English terminology). The visbreaking step is carried out at a temperature generally of between 370 ° C. and 500 ° C., preferably between 420 ° C. and 480 ° C., for a period generally of between 1 and 60 minutes, preferably between 10 and 45 minutes, total pressure generally less than 10 MPa, preferably less than 5 MPa and more preferably less than 2 MPa. The cracking rate is controlled by adjusting the residence time of the hydrocarbons in the ripening chamber. A quench (quench according to the English terminology) of the effluent is then generally performed and the cracked products are separated by a rapid distillation (flash distillation according to the English terminology) and possibly by steam stripping. Such a method is for example described in the patents US 7,220,887 B2 and US 7,193,123 B2 or in the magazine " Petroleum Refining "Volume 3, Chapter 11, Technip Editions . Such a visbreaking residue process is for example the TERVAHL process marketed by the company Axens.

It is possible to hydrotreat the feedstock upstream of the visbreaking stage in order to obtain better quality products, in particular with a low sulfur content. It is therefore preferable to add a hydrotreating step (eg for example a hydrodesulphurization and / or hydrodenitrogenation step) just before the visbreaking step a) in order to increase the degree of saturation of the hydrocarbons, while partly eliminating the sulfur or nitrogen compounds. Such a process for the hydrotreatment of residues is, for example, the HYVAHL process marketed by the company Axens.

In a variant of the process according to the invention, the visbreaking stage is operated in the presence of hydrogen (hydrovisbreaking according to the English terminology), which simultaneously allows saturation and cracking of hydrocarbons. In fact, the visbreaking of a hydroprocessed feedstock (that is to say in which the content of saturated hydrocarbons is greater) makes it possible to obtain higher conversion rates during the visbreaking step. Such visbreaking technologies in the presence of hydrogen are therefore preferred in the context of the present process, insofar as they avoid the addition of an additional hydrotreatment stage, while making it possible to obtain a quality of the effluents of this process. very satisfactory stage. It is also possible to operate a visbreaking process in the presence of hydrogen using a hydrogen donor solvent, as described for example in the patent US 4,592,830 .

The operating conditions that can be used in visbreaking processes in the presence of hydrogen are, for example, cited in the patent of Philips Petroleum. US 4,708,784 and in patents US 4,533,462 , EP 0 113 284 B and EP 0 649 896 B .

The conversion rate of the compounds boiling above 540 ° C in the feedstock during the visbreaking step a) is generally less than 60%, preferably less than 50% and more preferably less than 45%.

Step b) : Separation of the visbreaking effluent

The effluent obtained at the end of the visbreaking step a) may undergo at least one separation step, possibly supplemented by further additional separation steps, making it possible to separate at least one light fraction of hydrocarbons containing fuel bases and a heavy fraction containing boiling compounds at least 350 ° C.

The separation step may advantageously be carried out by any method known to those skilled in the art such as, for example, the combination of one or more high and / or low pressure separators, and / or distillation stages and / or or high and / or low pressure stripping, and / or liquid / liquid extraction steps. Preferably, the separation step b) makes it possible to obtain a gaseous phase, at least a light fraction of hydrocarbons of the naphtha, kerosene and / or diesel type, a vacuum distillate fraction and a vacuum residue fraction and / or a fraction of atmospheric residue.

The complexity of the separation step depends on the complexity of the visbreaking step a), especially if this visbreaking step operates under pressure and / or in the presence of hydrogen.

In the case of an implementation of the visbreaking step in the absence of hydrogen and at low pressure (less than 2 MPa), the effluent of the visbreaking step a) is introduced into a distillation column allowing recovering at least one gaseous fraction and a liquid fraction of atmospheric residue type. Most often this column also makes it possible to withdraw an unstabilized naphtha-type cut (which will optionally be subsequently treated in a stabilization column) as a liquid distillate at the reflux flask. Most often this column also allows laterally withdrawing a fraction of the diesel type, possibly with a lateral stripper. The liquid fraction of the atmospheric residue type can optionally be treated in a vacuum column to recover a vacuum distillate and a vacuum residue.

In the case of an implementation of the visbreaking step in the presence of hydrogen, the effluent from the visbreaking step is at high pressure and contains at least one gas phase and a liquid phase. Thus, the separation can be carried out in a fractionation section which can firstly comprise a high temperature high pressure separator (HPHT), and optionally a low temperature high pressure separator (HPBT), and / or atmospheric distillation and / or vacuum distillation. During step b), the effluent obtained at the end of step a) is advantageously separated in a HPHT high-pressure high-temperature separator into a light fraction and a heavy fraction containing predominantly at least 350 boiling compounds. ° C. The cutting point of the separation is advantageously between 200 and 400 ° C.

In a variant of the process of the invention employing hydrogen during the visbreaking stage, the effluent resulting from the visbreaking step a) may, during step b), also undergo a succession instantaneous separation device (or flash according to the English terminology) comprising at least one high temperature high pressure balloon (HPHT) and a high temperature low pressure balloon (BPHT) for separating a heavy fraction which is sent in a stripping step to the steam for removing from said heavy fraction at least a light fraction rich in hydrogen sulfide. The heavy fraction recovered at the bottom of the stripping column contains compounds boiling at least 350 ° C. but also atmospheric distillates. According to the process of the invention, said heavy fraction separated from the light fraction rich in hydrogen sulphide is then sent to the maturation step c) and then to the sediment separation step d).

In a variant, at least a portion of the so-called heavy fraction from step b) is fractionated by atmospheric distillation into at least one atmospheric distillate fraction containing at least one light fraction of naphtha, kerosene and / or diesel type hydrocarbons. and an atmospheric residue fraction. At least a part of the atmospheric residue fraction can be sent in the maturation step c) and then in the sediment separation step d).

The atmospheric residue may also be at least partially fractionated by vacuum distillation into a vacuum distillate fraction containing vacuum gas oil and a vacuum residue fraction. Said fraction vacuum residue is advantageously sent at least partly in the maturation step c) and then in the sediment separation step d).

At least a portion of the vacuum distillate and / or vacuum residue may also be recycled to the visbreaking step a).

Whatever the method of separation used, the light fraction (s) obtained may (may) undergo further separation steps. Advantageously, it (s) is (are) subject (s) to atmospheric distillation to obtain a gaseous fraction, at least a light fraction of naphtha, kerosene and / or diesel type hydrocarbons and a vacuum distillate fraction.

Part of the atmospheric distillate and / or vacuum distillate may be part of a fuel oil as a fluxing agent. These cuts can also be marine fuels with low viscosity (MGO or MGO, Marine Diesel Oil or Marine Gas Oil according to English terminology). Another part of the vacuum distillate can still be upgraded by hydrocracking and / or catalytic cracking in a fluidized bed.

The gaseous fractions resulting from the separation step preferably undergo a purification treatment to recover the hydrogen or hydrogen and recycle it.

The recovery of different fuel base cuts (LPG, naphtha, kerosene, diesel and / or vacuum gas oil) obtained from the present invention is well known to those skilled in the art. The products obtained can be integrated in fuel tanks (also called "pools" fuels according to the English terminology) or undergo additional refining steps. The fraction (s) naphtha, kerosene, gas oil and vacuum gas oil may be subjected to one or more treatments (hydrotreatment, hydrocracking, alkylation, isomerization, catalytic reforming, catalytic cracking or thermal or other) to bring them to the specifications. required (sulfur content, smoke point, octane, cetane, etc ...) separately or in mixture.

Advantageously, the vacuum distillate leaving the visbreaking after separation can be hydrotreated.

This hydrotreated vacuum distillate may be used as a fluxing agent for the fuel oil pool having a sulfur content of less than or equal to 0.5% by weight or may be used directly as oil with a sulfur content of less than or equal to 0.1% by weight.

Part of the atmospheric residue, vacuum distillate and / or vacuum residue may undergo further refining steps, such as hydrotreatment, hydrocracking, or fluidized catalytic cracking.

Step c) : Maturation of sediments

The heavy fraction obtained at the end of the separation step b) contains organic sediments which result from visbreaking conditions. Part of the sediment consists of asphaltenes precipitated under visbreaking conditions and are analyzed as existing sediments (IP375) and another part is formed after aging (IP390), aging causing additional precipitation.

Depending on the visbreaking conditions, the sediment content in the heavy fraction varies. From an analytical point of view, existing sediments (IP375) and sediments after aging (IP390) are distinguished from potential sediments. However, depending on the nature of the load and visbreaking conditions more or less severe, that is to say when the conversion rate (compounds boiling above 540 ° C in the load) is for example higher at 40 or 50%, existing sediments and potential sediments are formed.

In order to obtain a fuel oil or a fuel base that meets the recommendations for a sediment content after aging (IP390) of less than or equal to 0.1%, the process according to the invention comprises a maturation stage making it possible to improve the sediment separation efficiency and thus to obtain stable oil or fuel bases, that is to say a sediment content after aging less than or equal to 0.1% by weight.

The maturation step according to the invention makes it possible to form all the existing and potential sediments (by converting the potentials into existing ones) in such a way as to separating more efficiently and thus respect the sediment content after aging (IP390) by 0.1% maximum weight.

The maturation step according to the invention is advantageously carried out for a residence time of between 1 and 1500 minutes, preferably between 25 and 300 minutes, more preferably between 60 and 180 minutes, at a temperature between 50 and 350 ° C, preferably between 75 and 300 ° C and more preferably between 100 and 250 ° C. The pressure of the maturation stage is advantageously less than 20 MPa, preferably less than 10 MPa, more preferably less than 3 MPa and even more preferably less than 1.5 MPa.

The ripening conditions are mild enough not to cause excessive hydrocarbon conversion. During the maturation step, the conversion rate of the compounds boiling above 540 ° C. is less than 10%, preferably less than 5% and more preferably less than 2%.

The ripening step may be carried out using an exchanger or a heating furnace followed by one or more capacity (s) in series or in parallel such (s) as a horizontal or vertical balloon, optionally with a settling function to remove some of the heavier solids, and / or a piston reactor. A stirred and heated tank may also be used, and may be provided with a bottom draw to remove some of the heavier solids.

Advantageously, step c) of maturation of the heavy fraction resulting from step b) is carried out in the presence of an inert gas and / or an oxidizing gas.

The curing step c) can be carried out in the presence of an inert gas (for example nitrogen) or an oxidizing gas (oxygen for example), or in the presence of a mixture containing an inert gas and an oxidizing gas such as air or the air depleted by nitrogen. The use of an oxidizing gas accelerates the maturation process. According to this option, there is therefore introduction of a gas mixed with the liquid fraction from step b) before the maturation and separation of this gas after maturation so as to obtain a liquid fraction at the end of the step c) ripening. Such a gas / liquid implementation can for example be carried out in a bubble column. According to one variant, the inert and / or oxidizing gas may also be introduced during the c) stage of maturation, for example by means of bubbling (injection of gas from below) into a stirred tank, which makes it possible to promote gas / liquid contact.

At the end of the curing step c), at least one hydrocarbon fraction with an enriched content of existing sediments is obtained which is sent to step d) of separation of the sediments.

Step d) : Separation of sediments

The method according to the invention further comprises a step d) of separating the sediments.

The heavy fraction obtained at the end of the curing step c) contains precipitated asphaltene-type organic sediments which result from the visbreaking and maturation conditions.

Thus, at least a portion of the heavy fraction resulting from the curing step c) is subjected to a separation of the sediments, by means of at least one physical separation means chosen from a filter, a separation membrane, a bed organic or inorganic type filter solids, electrostatic precipitation, centrifugation system, decantation, auger withdrawal. A combination, in series and / or in parallel, of several separation means of the same type or different type can be used during this step d) separation of sediments and catalyst residues. One of these solid-liquid separation techniques may require the periodic use of a light rinsing fraction, resulting from the process or not, allowing for example the cleaning of a filter and the evacuation of sediments.

The heavy fraction resulting from step d) with a reduced sediment content can advantageously be used as a base for fuel oil or as fuel oil, in particular as a bunker oil or bunker oil base, having a sediment content after aging of less than 0, 1% weight Advantageously, said heavy fraction is mixed with one or more fluxing bases selected from the group consisting of catalytic cracking light cutting oils, catalytic cracking heavy cutting oils, catalytic cracking residue, kerosene, diesel fuel, a vacuum distillate and / or a decanted oil.

Step e) optional : optional separation step

The effluent obtained at the end of step d) of separation of the sediments can undergo an optional separation step making it possible to separate at least a light fraction of hydrocarbons containing fuels bases and a heavy fraction containing predominantly at least 350 ° C.

This separation step can advantageously be carried out by any method known to those skilled in the art such as, for example, the combination of one or more high and / or low pressure separators, and / or distillation and / or distillation stages. high and / or low pressure stripping. This optional step e) of separation is similar to the separation step b) and will not be further described.

Preferably, this separation step makes it possible to obtain at least a light fraction of hydrocarbons of the naphtha, kerosene and / or diesel type, a vacuum distillate fraction and a vacuum residue fraction and / or an atmospheric residue fraction.

Part of the atmospheric residue and / or the vacuum residue can also be recycled to the hydrocracking step a).

Step f) : Optional hydrotreatment step

The sulfur content of the heavy fraction resulting from step d) or e) when the latter is used, and containing predominantly compounds boiling at least 350 ° C is a function of the operating conditions of the visbreaking stage but also and especially of the sulfur content of the original charge.

Thus, for fillers with a low sulfur content, generally less than 1% by weight, preferably less than 0.5% by weight, it is possible to directly obtain a heavy fraction with less than 0.5% by weight of sulfur, such as required for ships without smoke treatment and operating outside the ZCSEs by 2020-2025.

For more sulfur-containing fillers, whose sulfur content is generally greater than 1% by weight, preferably greater than 0.5% by weight, the sulfur content of the heavy fraction may exceed 0.5% by weight. In such a case, a step f) of hydrotreatment in a fixed bed is made necessary in the case where the refiner wishes to reduce the sulfur content, in particular for a bunker oil base or a bunker oil intended to be burned on a ship without smoke treatment.

According to the invention, the hydrotreating step described in step f) is identical to the step of hydrotreatment of the charge advantageously carried out before the visbreaking step. In the case where a step of hydrotreatment of the feedstock is carried out prior to the visbreaking step, the conditions described in step f) are therefore transferable to this hydrotreatment step.

The f) fixed bed hydrotreatment step is carried out on at least a portion of the heavy fraction resulting from step d) or e) when step e) is implemented. The heavy fraction from step f) can advantageously be used as a base of fuel oil or as fuel oil, especially as a base of bunker oil or as bunker oil, having a sediment content after aging less than 0.1% by weight. Advantageously, said heavy fraction is mixed with one or more fluxing bases selected from the group consisting of catalytic cracking light cutting oils, catalytic cracking heavy cutting oils, catalytic cracking residue, kerosene, a gas oil, a vacuum distillate and / or a decanted oil.

The heavy fraction resulting from the sediment separation step d) or e) when step e) is carried out is sent to the hydrotreatment step f) comprising one or more hydrotreatment zones in fixed beds. The sending in a fixed bed of a heavy fraction devoid of sediments constitutes an advantage of the the present invention since the fixed bed will be less subject to clogging and increased pressure drop.

Hydroprocessing (HDT) is understood to mean, in particular, hydrodesulphurization (HDS) reactions, hydrodenitrogenation (HDN) reactions and hydrodemetallation (HDM) reactions, but also hydrogenation, hydrodeoxygenation, hydrodearomatization, hydrodenetration, hydroisomerization, hydrodealkylation, hydrocracking, hydro-deasphalting and Conradson carbon reduction.

Such a method of hydrotreating heavy cuts is widely known and can be related to the process known as HYVAHL-F ™ described in US Pat. US5417846 .

The person skilled in the art easily understands that in the hydrodemetallization stage, hydrodemetallation reactions are mainly carried out but also part of the hydrodesulfurization reactions. Similarly, in the hydrodesulfurization step, hydrodesulphurization reactions are mainly carried out but also part of the hydrodemetallation reactions.

According to one variant, a co-charge may be introduced with the heavy fraction in the hydrotreatment step f). 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 process of fluid catalytic cracking in a fluid bed: a light cutting oil (LCO), a heavy cutting oil (HCO), a decanted oil, or possibly derived from distillation, the gasoil fractions in particular those obtained by atmospheric or vacuum distillation, such as, for example, vacuum gas oil.

The hydrotreatment step may advantageously be carried out at a temperature of between 300 and 500 ° C., preferably 350 ° C. to 420 ° C. and under a hydrogen partial pressure advantageously of between 5 MPa and 25 MPa. preferably between 10 and 20 MPa, a global space velocity (VVH) ranging from 0.1 hr -1 to 5 hr -1 and preferably from 0.1 hr -1 to 2 hr -1, a quantity of hydrogen mixed with the feedstock usually of 100 to 5000 Nm3 / m3 (normal cubic meters (Nm3) per cubic meter (m3) of liquid load), most often from 200 to 2000 Nm3 / m3 and preferably from 300 to 1500 Nm3 / m3.

Usually, the hydrotreating step is carried out industrially in one or more liquid downflow reactors. The hydrotreatment temperature is generally adjusted according to the desired level of hydrotreatment.

The hydrotreatment catalysts used are preferably known catalysts and are generally granular catalysts comprising, on a support, at least one metal or metal compound having a hydrodehydrogenating function. These catalysts are advantageously catalysts comprising at least one Group VIII metal, generally selected from the group consisting of nickel and / or cobalt, and / or at least one Group VIB metal, preferably 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 of molybdenum, preferably from 5 to 20% by weight of molybdenum (expressed as molybdenum oxide MoO ₃ ) on a mineral support. This support will, for example, be selected from the group formed by alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. Advantageously, this support contains other doping compounds, in particular oxides chosen from the group formed by 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. The concentration of phosphorus pentoxide P ₂ O ₅ is usually between 0 or 0.1% and 10% by weight. The concentration of boron trioxide B ₂ O ₅ is usually between 0 or 0.1% and 10% by weight. The alumina used is usually a γ or η alumina. This catalyst is most often in the form of extrudates. The total content of oxides of Group VIB and VIII metals is often 5 to 40% by weight and generally 7 to 30% by weight and the weight ratio expressed as metal oxide between group VIB metal (or metals) on metal (or metals) of the group VIII is in general from 20 to 1 and most often from 10 to 2.

In the case of a hydrotreatment step including a hydrodemetallation step (HDM), then a hydrodesulfurization step (HDS), it is most often used specific catalysts adapted to each step.

Catalysts that can be used in the hydrodemetallation (HDM) stage are for example indicated in the patents EP113297 , EP113284 , US5221656 , US5827421 , US7119045 , US5622616 and US5089463 . Hydrodemetallation (HDM) catalysts are preferably used in the reactive reactors. Catalysts that can be used in the hydrodesulfurization (HDS) step are, for example, indicated in the patents EP113297 , EP113284 , US6589908 , US4818743 or US6332976 . It is also possible to use a mixed catalyst that is active in hydrodemetallization and in hydrodesulfurization for both the hydrodemetallation (HDM) section and the hydrodesulfurization (HDS) section as described in the patent. FR2940143 .

Prior to the injection of the feed, the catalysts used in the process according to the present invention are preferably subjected to an in-situ or ex-situ sulphurization treatment .

Step g) : Optional step of separation of the hydrotreatment effluent

The optional separation step g) may advantageously be carried out by any method known to those skilled in the art such as, for example, the combination of one or more high and / or low pressure separators, and / or distillation and / or high and / or low pressure stripping. This optional separation step g) is similar to the separation step b) and will not be further described.

In an alternative embodiment of the invention, the effluent obtained in step f) is at least partly, and often in all, sent to a separation step g), comprising atmospheric distillation and / or vacuum distillation. The effluent of the hydrotreatment stage is fractionated by atmospheric distillation into a gaseous fraction, at least one atmospheric distillate fraction containing the fuels bases (naphtha, kerosene and / or diesel) and an atmospheric residue fraction. At least a portion of the atmospheric residue can then be fractionated by vacuum distillation into a vacuum distillate fraction containing vacuum gas oil and a vacuum residue fraction.

The vacuum residue fraction and / or the vacuum distillate fraction and / or the atmospheric residue fraction can in part constitute at least the bases of low sulfur fuel oils having a sulfur content of less than or equal to 0.5 wt% and a sediment content after aging less than or equal to 0.1%. The vacuum distillate fraction can constitute a fuel oil base having a sulfur content of less than or equal to 0.1% by weight.

Part of the vacuum residue and / or the atmospheric residue may also be recycled to the visbreaking step a).

fluxing

To obtain a fuel oil, the heavy fractions resulting from steps d) and / or e) and / or f) and / or g) can be mixed with one or more fluxing bases chosen from the group consisting of light cutting oils. catalytic cracking, catalytically cracked heavy cutting oils, catalytic cracking residue, kerosene, gas oil, vacuum distillate and / or decanted oil. Preferably, kerosene, gas oil and / or vacuum distillate produced in the process of the invention will be used. Advantageously, use will be kerosene, gas oil and / or vacuum distillate obtained (s) in the separation steps b) or g) of the process.

EXAMPLES

The following example illustrates the invention without limiting its scope. The treated feed is a vacuum residue (RSV Ural) whose characteristics are shown in Table 1. <u> Table 1: Characteristics of the load </ u> Chopped off RSV Urals Sulfur% mass 2.7 Conradson Carbon 16 Asphalenes C7 (% by mass) 4.2 NI + V ppm 220 Viscosity at 100 ° C (cSt) 548 350 ° C + (% mass of compounds boiling above 350 ° C) 99.0 540 ° C + (% mass of compounds boiling above 540 ° C) 86.5

The filler is subjected to a visbreaking step. The operating conditions of the visbreaking section are given in Table 2. <u> Table 2: Operational conditions visbreduction section </ u> Oven outlet temperature (° C) 457 Total pressure, MPa 0.8 Time of stay maturation room (minutes) 35

1. A) Pas de traitement supplémentaire (non-conforme à l'invention),
2. B) Une étape de maturation des sédiments (4h à 150°C réalisée dans une cuve agitée chauffée en présence d'un mélange air/azote 50/50 sous une pression totale de 0,5 MPa) puis une étape de séparation physique des sédiments à l'aide d'un filtre (conforme à l'invention).

The visbreaking effluents are then subjected to a separation comprising an atmospheric distillation and making it possible to recover a gaseous fraction and a heavy fraction. The heavy fraction (350 ° C + fraction) is then treated according to two variants:

1. A) No additional treatment (not in accordance with the invention),
2. B) A stage of sediment maturation (4 h at 150 ° C. carried out in a stirred tank heated in the presence of a 50/50 air / nitrogen mixture under a total pressure of 0.5 MPa) and then a step of physical separation of the sediments using a filter (according to the invention).

According to the two previous variants A) and B), the 350 ° C. fractions are distilled in the laboratory in order to know the qualities and yields of vacuum distillate and vacuum residue. Yields as well as sulfur content and viscosity (for heavy cuts) are shown in Table 3. <u> Table 3: Yields, sulfur content and visbreaking viscosity section </ u> Yield (% weight / load) Sulfur content (% by weight) Viscosity at 100 ° C (cSt) Gas 4.2 Naphtha (80-180 ° C) 2.8 Diesel (180-350 ° C) 7.5 Vacuum distillates (350-540 ° C) 39.4 Vacuum residue (540 + ° C) 46.2 Atmospheric residue (350 ° C +, Charge of the ripening stage) 85.6 2.3 85

The operating conditions of the visbreduction stage coupled to a stage of maturation and separation of the sediments according to the invention carried out on the heavy fraction resulting from the atmospheric distillation have an impact on the stability of the effluents obtained. This is illustrated by the sediment contents after aging measured in atmospheric residues (350 ° C + cut). The performance is summarized in Table 4 below. <u> Table 4: Summary of performance with or without sediment ripening and separation </ u> visbreaking Conversion rate of compounds boiling above 540 ° C (%) 46 Maturation No Yes Separation of sediments No Yes Sediment content after aging (IP390) in the 350 ° C + section 0.6 <0.1

According to the invention, it is possible to obtain stable effluents with a low sediment content as soon as a maturation step and then a sediment separation step are implemented.

It is also possible to subject the effluents from the ripening and sediment separation stages to a fixed bed hydrotreatment stage. The operating conditions of the hydrotreatment step are shown in Table 5.

The CoMoNi catalysts used on Alumina are sold by Axens under the references HF858, HM848 and HT438. <u> Table 5: Operating Conditions of the Hydrotreatment Stage Performed on the 350+ Cups Resulting from the Visbreduction Stage After Passing to the Maturation and Sediment Separation Stage </ u> HDM, transition and HDS catalysts CoMoNi on alumina Cycle start temperature (° C) 370 H2 partial pressure (MPa) 15 VVH (h-1, Sm3 / h fresh load / m3 fixed bed catalyst) 0.16 H2 / HC inlet section fixed bed excluding H2 consumption (Nm3 / m3 fresh load) 1000

The effluents from the hydrotreating step are then separated and analyzed. The vacuum distillate fractions contain less than 0.2% by weight of sulfur. The fractions under vacuum contain less than 0.5% by weight of sulfur. Thus, vacuum distillate fractions and vacuum residues (or atmospheric residue fractions) with low sulfur content and low sediment content after aging are obtained. These fractions thus constitute excellent fuel oil bases and in particular excellent fuel oil bases.

Claims (14)

A process for converting a hydrocarbon feedstock containing at least one hydrocarbon fraction having a sulfur content of at least 0.1% by weight, an initial boiling temperature of at least 340 ° C and a final temperature of boiling at least 440 ° C to obtain a heavy fraction having a sediment content after aging less than or equal to 0.1% by weight, said process comprising the following steps: a) a visbreaking step of the charge in at least one maturation chamber, b) a step of separating the effluent obtained at the end of step a) into at least a light hydrocarbon fraction containing fuels bases and a heavy fraction containing compounds boiling at least 350 ° C, c) a step of maturation of the heavy fraction resulting from the separation stage b) allowing the transformation of a part of the potential sediments into existing sediments, carried out for a period of between 1 and 1500 minutes, at a temperature of between 50 and and 350 ° C, and a pressure of less than 20 MPa, d) a step of separating the sediments from the heavy fraction resulting from the curing step c) to obtain said heavy fraction. The process according to claim 1 wherein the visbreaking step is carried out at a temperature between 370 ° C and 500 ° C, for a period of between 1 and 60 minutes, a total pressure of less than 10 MPa. Process according to either of Claims 1 and 2, in which a step of hydrotreatment of the feed is carried out upstream of the visbreaking step a). Method according to one of the preceding claims wherein the visbreaking step is carried out in the presence of hydrogen. Process according to one of the preceding claims, in which, during stage b), the effluent obtained at the end of stage a) is separated in a HPHT high temperature high pressure separator into a light fraction and a heavy fraction. containing predominantly boiling compounds at least 350 ° C. Process according to one of the preceding claims, in which at least a portion of the so-called heavy fraction resulting from step b) is fractionated by atmospheric distillation into at least one atmospheric distillate fraction containing at least one light fraction of naphtha-type hydrocarbons. , kerosene and / or diesel and an atmospheric residue fraction. Process according to one of the preceding claims wherein the step of maturation of the heavy fraction resulting from step b) is carried out in the presence of an inert gas and / or an oxidizing gas. Process according to one of the preceding claims wherein the separation step d) is carried out by means of at least one separation means chosen from a filter, a separation membrane, a bed of organic or inorganic type filtering solids, electrostatic precipitation, a centrifugation system, decantation, auger withdrawal. Process according to one of the preceding claims, further comprising a step f) of fixed bed hydrotreatment carried out on at least part of the heavy fraction resulting from step d) in which, under the conditions of hydrotreatment, the heavy fraction and hydrogen on a hydrotreatment catalyst. A process according to claim 9 wherein the hydrotreatment step is carried out at a temperature between 300 and 500 ° C, an absolute pressure of between 5 MPa and 25 MPa, a global hourly space velocity (VVH) lying in a range ranging from 0.1 h ^-1 to 5 h ^-1 , a quantity of hydrogen mixed with the feed of 100 to 5000 Nm ³ / m ³ . A process according to claim 9 or 10 wherein a co-charge is introduced with the heavy fraction in the hydrotreatment step f). Process according to claim 11, in which the co-charge is chosen from atmospheric residues, vacuum residues from direct distillation, deasphalted oils, aromatic extracts from lubricant base production lines, hydrocarbon fractions or a mixture hydrocarbon fractions which may be chosen from products derived from a fluid-bed catalytic cracking process: a light cutting oil (LCO), a heavy cutting oil (HCO), a decanted oil, or possibly derived from distillation, gas oil fractions, especially those obtained by atmospheric or vacuum distillation, such as, for example, vacuum gas oil. Process according to one of the preceding claims, in which the treated filler is chosen from atmospheric residues, vacuum residues resulting from direct distillation, crude oils, crude head oils, deasphalted oils, deasphalting resins, asphalts or deasphalting pitches, residues resulting from conversion processes, aromatic extracts from lubricant base production lines, oil sands or their derivatives, oil shales or their derivatives, whether alone or in combination. Process according to one of the preceding claims in which the heavy fractions resulting from steps d) and / or f) are mixed with one or more fluxing bases chosen from the group consisting of catalytically cracked light cutting oils, the oils heavy catalytic cracking fraction, catalytic cracking residue, kerosene, gas oil, vacuum distillate and / or decanted oil.