FR3036704A1 - METHOD FOR CONVERTING LOADS COMPRISING A VISCOREDUCTION STEP, A PRECIPITATION STEP AND A SEDIMENT SEPARATION STEP FOR FIELD PRODUCTION - Google Patents

Abstract

The invention relates to a process for converting a hydrocarbon feedstock, said process comprising the following steps: a) a visbreaking step of the feedstock, b) a step of separating the effluent obtained at the end of the step a), c) a sediment precipitation step in which the heavy fraction resulting from the separation step b) is brought into contact with a distillate cut of which at least 20% by weight has a boiling point greater than or equal to 100 ° C, for a period of less than 500 minutes, at a temperature between 25 and 350 ° C, and a pressure of less than 20 MPa, d) a step of physical separation of the sediments of the heavy fraction resulting from step c) of precipitation to obtain said heavy fraction separated from the sediments, e) a step of recovering a heavy fraction having a sediment content, measured according to the ISO 10307-2 method, less than or equal to 0.1% by weight.

Description

The present invention relates to the refining and conversion of heavy hydrocarbon fractions containing, inter alia, sulfur 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 (Cl to C4). The quality requirements for marine fuels are described in ISO 8217. The sulfur specification now focuses on SOx emissions (Annex VI of the MARPOL Convention of the International Maritime Organization) and results in a recommendation in terms of quality. Sulfur less than or equal to 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% by weight in the ZCESCs. 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 after aging is a measurement carried out according to the method described in the ISO 10307-2 standard (also known to those skilled in the art under the name of IP390). In the rest of the text will therefore read "sediment content after aging", the sediment content measured according to the ISO 10307-2 method. The reference to IP390 will also indicate that the measurement of the sediment content after aging is performed according to the ISO 10307-2 method. 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 make it possible to convert low value residues into 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 bubbling bed residue hydrocracking process, 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 valorized as fuel oil, 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 effluents and allow them to operate at a higher severity.

The visbreaking process makes it possible to partially convert heavy charges 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, polycondensation, etc.) leading to their precipitation as soon as the conditions are severe and the conversion rate is high. for this type of 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 the sediments appear visbreduction is lower than in the 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's research has developed a new method incorporating a step of precipitation and physical separation of sediments downstream of a visbreaking stage. It has been found that such a process makes it possible to obtain heavy fractions having a low sediment content after aging according to ISO 10307-2, the said heavy fractions being advantageously able to be used wholly or partly as fuel oil or as fuel oil base. According to the future specifications, namely a sediment content after aging (measured according to the ISO 10307-2 method) less than or equal to 0.1% by weight. 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 point of at least 340 ° C and a final boiling point of not less than 440 ° C said method comprising the following steps a) a visbreaking step of the feedstock in at least one matning chamber, b) a step of separating the effluent obtained at the end of e step a) into at least a light hydrocarbon fraction containing fuel bases and a heavy fraction containing compounds boiling at least 350 ° C, c) a sediment precipitation step in which the heavy fraction derived from the separation step b) is brought into contact with a distillate cut of which at least 20% by weight has a boiling point greater than or equal to 100 ° C., for a duration of less than 500 minutes, at a temperature of between 25.degree. and 350 ° C, and a pressure below 20 MPa, d) a step of physically separating the sediments of the heavy fraction from step c) of precipitation to obtain said heavy fraction separated from the sediments, e) a step of recovering a heavy fraction having a sediment content, measured according to the ISO 10307-2 method, less than or equal to 0.1% by weight of separating the heavy fraction resulting from step d) from the distil fraction lat introduced in step c).

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 making it possible to produce, especially by visbreaking, atmospheric distillates or vacuum distillates (naphtha, kerosene, diesel, vacuum distillate) which can be used as bases in the pools. Fuels can be used directly or after passing through another refining process such as hydrotreating, reforming, isomerization-hydrocracking or catalytic cracking. FIG. 1 is a schematic view of the process according to the invention showing a visbreaking zone, a separation zone, a precipitation zone, a physical separation zone of the sediments and a recovery zone of the fraction of interest. The heats treated in the process according to the invention are advantageously chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, crude oils with head, deasphalted oils, resins of deasphalting, 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 mixtures . These fillers can advantageously be used as they are or else diluted by a hydrocarbon fraction or a mixture of hydrocarbon fractions which can be chosen from products resulting from a process for fluid catalytic cracking (FOC 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 possibly derived from distillation, gas oil fractions including those obtained by atmospheric or vacuum distillation, such as vacuum gas oil. The heavy charges may also advantageously comprise cuts resulting from the process of liquefying coal or biomass, aromatic extracts, or any other hydrocarbon cuts or non-petroleum feedstocks such as pyrolysis oil from lignocellulosic biomasses. 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 filler may contain at least 1% of asphaltenes 07 and at least 5 ppm of metals, preferably at least 2% of asphaltenes 07 and at least 25 ppm of metals. The fillers according to the invention are preferably atmospheric residues or residues under vacuum, or mixtures of these residues. Step a): Viscoréd The filler according to the invention is subjected to a visbreaking step 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 soaker chamber according to the English terminology. The visbreaking step is carried out at a temperature generally 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. a 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. Quenching (quenching according to the English terminology) of the effluent is then generally carried out and the cracked products are separated by a rapid distillation (flash distillation according to the English terminology) and possibly by steam stripping. Such a process is for example described in US Pat. No. 7,220,887 B2 and US Pat. No. 7,193,123 B2 or in the journal "Petroleum Refining", Volume 3, Chapter 11, Technip Publishing. 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 step in order to obtain better quality products, especially with low sulfur content. It is therefore preferable to add a hydrotreatment step (for example a hydrodesulphurization and / or hydrodenitization step) just before the visbreaking step a) in order to increase the saturation rate of the hydrocarbons, while partially eliminating 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 step is carried out 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 feed (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 US Pat. No. 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 Petroleunn US 4,708,784 and in US Pat. Nos. 4,533,462, EP 0 113 284 B and EP 0 649 896 B. The conversion of compounds boiling above 540 ° C into 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 Visbreduction Effluent The effluent obtained at the end of the visbreaking step a) can undergo at least one separation step, possibly completed by additional separation steps, allowing separating at least a light fraction of hydrocarbons containing fuels 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 and distillation stages. and / 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. or an atmospheric residue fraction. In such a case, the heavy fraction sent in the precipitation step c) corresponds at least in part to an atmospheric residue fraction. 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 fraction (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 atmospheric residue liquid fraction may 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 e.1 sent in a step of steam stripping for removing from said heavy fraction at least a light fraction rich in hydrogen sulfide. The recovered heavy fraction 3036704 8 at the bottom of the stripping column contains compounds boiling at least 350 ° C but also atmospheric distillates. According to the method of the invention, said heavy fraction separated from the light fraction rich in hydrogen sulphide is then sent to the precipitation step c) and then to the step of physically separating sediments d).

Alternatively, at least a part of the so-called heavy fraction from step b) is fractionated by atmospheric distillation into at least one atmospheric distillate fraction containing at least a light fraction of naphtha, kerosene and / or diesel and a fraction of atmospheric residue. At least a portion of the atmospheric residue fraction, at least in part corresponding to the heavy fraction from step b), can be sent to the precipitation step c) and then to the step of physically separating the sediment from the sediment. ). The atmospheric residue may also be at least partially fractionated by vacuum distillation into a vacuum distillate fraction containing vacuum under vacuum and a vacuum residue fraction. Said fraction vacuum residue, corresponds to the heavy fraction resulting from step b), is advantageously sent at least partly in the precipitation step c) and then in the step of physical separation of sediments d). At least a portion of the vacuum distillate and / or vacuum residue may also be recycled to the visbreaking step a). Irrespective of the separation method 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 constitute 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 from the separation step preferably undergo a purification treatment to optionally recover the hydrogen and recycle it. Part of the purified hydrogen can be used during the precipitation step.

3036704 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 into 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 can be (are) subjected to one or more treatments (hydrotreatment, hydrocracking, alkylation, isomerization, catalytic reforming, catalytic or thermal cracking or other ) to bring them to the required specifications (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. A portion of the atmospheric residue, vacuum distillate, and / or vacuum residue may be subjected to additional refining steps, such as hydrotreating, hydrocracking, or fluidized catalytic cracking. And this Prl; cipit.a -; the sediment The heavy fraction obtained at the end of the separation step b) contains organic sediments which result from the visbreaking conditions. Part of the sediments consist of asphaltenes precipitated under visbreaking conditions and are analyzed as existing sediments (IP375). 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 feedstock 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 above 40 or 50%, existing sediments and potential sediments are formed. In order to obtain a fuel oil or oil base meeting the recommendations of a sediment content after aging (measured according to the ISO 10307-2 method) less than or equal to 0.1% by weight, the process according to the invention comprises a precipitation step making it possible to improve the sediment separation efficiency and thus to obtain stable fuel oils or oil bases, ie with a sediment content after aging less than or equal to 0.1 % in weight. The precipitation step according to the invention makes it possible to form all the existing and potential sediments (by converting the potentials into existing ones) so as to separate them more efficiently and thus to respect the sediment content after aging (measured according to the method ISO 10307-2) of 0.1% maximum weight. The precipitation step according to the invention comprises bringing the heavy fraction coming from the separation step b) into contact with a distillate cut of which at least 20% by weight has a boiling point greater than or equal to 100 ° C, preferably greater than or equal to 120 ° C, more preferably greater than or equal to 150 ° C. In a variant according to the invention, the distillate cut is characterized in that it comprises at least 25% by weight having a boiling point greater than or equal to 100 ° C., preferably greater than or equal to 120 ° C. more preferably greater than or equal to 150 ° C. Advantageously, at least 5% by weight or even 10% by weight of the distillate cut according to the invention has a boiling point of at least 252 ° C. More advantageously, at least 5 wt.% Or even 10 wt.% Of the distillate cut according to the invention has a boiling point of at least 255 ° C.

The precipitation step c) according to the invention is advantageously carried out for a residence time of less than 500 minutes, preferably less than 300 minutes, more preferably less than 60 minutes, at a temperature between 25 and 350 minutes. ° C, preferably between 50 and 350 ° C, preferably between 65 and 300 ° C and more preferably between 80 and 250 ° C. The pressure of the precipitation step 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 distillate cut according to the invention advantageously comprises hydrocarbons having more than 12 carbon atoms, preferably hydrocarbons having more than 13 carbon atoms, more preferably hydrocarbons having between 13 and 40 carbon atoms, 3036704 11 Said distillate fraction can partly or entirely from the separation step b) of the invention or another refining process or another chemical process. Said distillate cut may be used in a mixture with a naphtha-type cut and / or a vacuum-type gas oil cut and / or vacuum residue. Said distillate fraction may be used in a mixture with the light fraction obtained after step b), the atmospheric distillate fraction resulting from step b) and / or the vacuum distillate fraction originating from the stage b) separation. In the case where the distillate cut according to the invention is mixed with another cut, a light fraction and / or a heavy fraction as indicated above, the proportions are chosen so that the resulting mixture respects the characteristics of the distillate cut according to the invention. The use of the distillate cut according to the invention has the advantage of avoiding the majority use of high value added cuts such as petrochemical cuts, naphtha ... The mass ratio between the distillate cut according to the invention and the heavy fraction obtained at the end of the separation step b) is between 0.01 and 100, preferably between 0.05 and 10, more preferably between 0.1 and 5, and even more preferably between 0.1 and 2. When the distillate cut according to the invention is at least drawn from the process, it is possible to accumulate this cut during a start-up period so as to reach the desired ratio.

The precipitation 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 possibly 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 bottom tapped to remove some of the heavier solids. Advantageously, the precipitation step can be carried out online, without buffer capacity, possibly using a static mixer. According to one variant, step c) of precipitation of the heavy fraction resulting from step b) is carried out in the presence of an inert gas and / or an oxidizing gas and / or an oxidizing liquid and / or hydrogen, preferably from the separation steps of the process of the invention, in particular from the separation step b).

The precipitation step c) can be carried out in the presence of an inert gas such as dinitrogen, or in the presence of an oxidizing gas such as oxygen, ozone or nitrogen oxides, or in the presence of a mixture containing an inert gas and an oxidizing gas such as air or air depleted by nitrogen, or in the presence of an oxidizing liquid to accelerate the precipitation process. The term "oxidizing liquid" means an oxygenated compound, for example a peroxide such as hydrogen peroxide, or an inorganic oxidizing solution such as a solution of potassium permanganate or a mineral acid such as sulfuric acid. According to this variant, the oxidizing liquid is then mixed with the heavy fraction resulting from the separation step b) and the distillate cut according to the invention during the implementation of step c). At the end of the precipitation 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) physically separating the sediments. The heavy fraction obtained at the end of the precipitation step c) contains precipitated asphaltene-type organic sediments which result from the visbreaking and precipitation conditions.

Thus, at least a portion of the heavy fraction from step c) of precipitation is subjected to sediment separation by means of at least one physical separation means selected from a filter, a separation membrane, a bed of organic or inorganic type filtering 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) sediment separation. 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.

At the end of step d) of physical separation of the sediments, the heavy fraction (with a sediment content after aging of less than or equal to 0.1% by weight) is obtained comprising a part of the distillate cut according to the invention introduced during step c). Etap 7: The recovery of the heavy fraction re of the d) step 5 According to the invention, the mixture resulting from the step d) is advantageously introduced in a step e) of recovery of the heavy fraction having a content sediment after aging less than or equal to 0.1% by weight, said step of separating the heavy fraction from step d) of the distillate cut introduced in step c). Step e) is a separation step similar to separation step b). Step e) can be implemented by means of separator balloon and / or distillate-type equipment so as to separate on the one hand at least part of the distillate cut introduced during step c). precipitation and on the other hand the heavy fraction having a sediment content after aging (measured according to the ISO 10307-2 method) less than or equal to 0.1% by weight.

Advantageously, a portion of the distillate cut separated from step e) is recycled to the precipitation step c). Said recovered heavy fraction may 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, a kerosene, a gas oil, a vacuum distillate and / or a decanted oil. According to a particular embodiment, part of the distillate cut according to the invention can be left in the sediment-reduced heavy fraction so that the viscosity of the mixture is directly that of a desired oil grade. for example 180 or 380 cSt at 50 ° C and so that the sediment content after aging (measured according to the ISO 10307-2 method) is less than 0.1% by weight. The sulfur content of the heavy fraction from step d) or e) and containing predominantly compounds boiling at least 350 ° C is a function of the operating conditions of the visbreaking 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 that do not have smoke treatment and operate outside the ZCEA by 2020-2025.

For higher sulfur feeds, the sulfur content of which 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 vessel with no flue gas treatment. Stage f) of hydrotreatment in a fixed bed is carried out on at least a part of the heavy fraction resulting from stage d) or e). According to the invention, the hydrotreating step described in step f) is identical to the step of hydrotreatment of the feed 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 below in step f) are therefore transferable to this hydrotreatment step. The heavy fraction resulting from step f) can advantageously be used as a base for fuel oil or as fuel oil, especially as a bunker oil or bunker oil base, having a sediment content after aging of 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 from step d) or e) is sent to the hydrotreatment step f) comprising one or more fixed bed hydrotreating zones. It is an advantage of the present invention to dispense a heavy fraction free of sediment into the fixed bed since the fixed bed will be less subject to clogging and increased loss of charge. Hydrotreatment (HDT) in particular hydrodesulfurization reactions (HDS), hydrodenitrogenation reactions (HDN) and hydrodemetallation reactions (HDM), but also hydrogenation, hydrodeoxygenation, hydrodearomatization, hydroisomerisation, 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 under the name HYVAHL-FTM described in US Pat. No. 5,417,846. One skilled in the art readily understands that in the hydrodemetallization step, hydrodemetallization 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. Alternatively, 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 fluid-bed catalytic cracking process: 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. 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 between 5 MPa and 25 MPa. preferably between 10 and 20 MPa, an overall hourly 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 charge usually of 100 to 5000 Nm3 / m3 (normal cubic meters (Nm3) per cubic meter (m3) of liquid charge), most often 200 to 2000 Nm3 / m3 and preferably 300 at 1500 Nm3 / m3 Usually, the hydrotreatment step is carried out industrially in one or more liquid downflow reactors. The hydrotreatment temperature is generally adjusted according to the desired level of conversion of hydrotreatment. The hydrotreatment catalysts used are preferably known catalysts. Generally, they are 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 nickel will be used. 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 selected 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 P2O5 is usually between 0 or 0.1% and 10% by weight. The concentration of boron trioxide B205 is usually from 0 to 0.1% to 10% by weight. The alumina used is usually a y or ri alumina. This catalyst is most often in the form of extrudates. The total content of metal oxides of groups VIB and VIII is often 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 in general from 20 to 1 and most often from 10 to 2. In the case of a hydrotreating 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 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 step (HDS) 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 hydrodemetallation and hydrodesulphurization for both the hydrodemetallation (HDM) section and the hydrodesulfurization (HDS) section as described in FR2940143.

Prior to 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 q): Optional step of seeding the hydrotreatment effluent The process according to the invention may comprise a step g) of separating the effluents from the hydrotreating step f). 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 an atmospheric distillation and / or vacuum distillation. The effluent of the hydrotreating step 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 may in part constitute at least the bases of low sulfur fuel oils having a sulfur content of less than or equal to 0.5% by weight. and a sediment content after aging less than or equal to 0.1% by weight. The vacuum distillate fraction may be a fuel 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).

To obtain a fuel oil, the heavy fractions from steps d) and / or e) and / or f) and / or g) may be mixed with one or more fluxing bases selected from the group consisting of light cutting oils. catalytic cracking, catalytic cracked heavy cutting oils, catalytic cracking residue, kerosene, gas oil, vacuum distillate and / or decanted oil, the distillate cut according to US Pat. invention. 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. DESCRIPTION OF THE FIGURE FIG. 1 depicts a simplified example of implementation of the invention without limiting its scope. The hydrocarbon feedstock (1) is sent to a visbreaking zone a) (step a)). The effluent (2) from the visbreaking zone a) is sent to a separation zone b) to obtain at least one gaseous fraction (3) and at least one heavy liquid fraction (4). This liquid fraction (4) is brought into contact with a distillate cut (5) during a precipitation step c) in zone c). The effluent (6) consisting of a heavy fraction and sediment is treated in a physical separation zone d) (step d)) making it possible to eliminate a fraction comprising sediments (8) and to recover a liquid hydrocarbon fraction ( 7) with reduced sediment content. The liquid hydrocarbon fraction (7) is then treated in a zone e) of recovery firstly of the liquid hydrocarbon fraction (10) having a sediment content after aging less than or equal to 0.1% by weight, and on the other hand a fraction (9) containing at least a portion of the distillate cut introduced in step c). EXAMPLES The following example illustrates the invention without however limiting its scope. The treated feed is a vacuum residue (RSV Ural) whose characteristics are shown in Table 1.

3036704 19 Table u: Characteristics of the reactor Section RSV Ural Sulfur (° / 0 mass) 2.7 Carbon Conradson 16 Asphaltenes C7 (mass%) 4.2 NI + V ppm 220 V - nsity 100 ° C (cSt1 548 350 ° C + (% mass of compounds boiling above 350 ° C) 99.0 86.5 540 ° C + (% mass of compounds) or above 540 ° C) The feed is subjected to a visbreaking step . The operating conditions of the visbreaking section are given in Table 2. Table 2: Operational conditions visbreduction section The visbreaking effluents are then subjected to a separation comprising an atmospheric distillation and making it possible to recover a gaseous fraction, distillate and a fraction. heavy (atmospheric residue, RA). The yields are shown in Table 3. Table 3: Viscoreduction Section Efficiencies Oven Output Temperature (° C) Total Pressure, MPa Residence Time Curing Room (minutes) Yield (% w / w) Gas 4.2 Naphtha ( 80-180 ° C) 2.8 Diesel (180-350 ° C) 7.5 Vacuum distillate (350-39.4540 ° C) Vacuum residue (540 + ° C) 46.2 3036704 20 The heavy fraction (350 ° C + fraction, ie, vacuum distillate (350-540 ° C) and vacuum residue (540 + ° C)) is then treated according to two variants: A) A variant 1 in which the heavy fraction undergoes no additional treatment (not in accordance with the invention), 5 B) A variant according to which the sediment precipitation step (in accordance with the invention) is carried out by stirring at 100 ° C. for 30 minutes the heavy fraction and a distillate cut, corresponding to a mixture 50 ° / 0/50% weight. The mixture is then subjected to a sediment separation step using a Pan® brand metal porous filter. This step of physical separation of the sediments is followed by a step of recovering the heavy fraction (distillation of the mixture making it possible to recover on the one hand the heavy fraction with reduced sediment content, and on the other hand the distillate cut) . The resulting diesel cut (180 ° -350 ° C) is used as the distillate cut for the precipitation step. This distilh cup, which is characterized by the simulated distillation which represents the distilled percentage as a function of temperature, contains more than 5% by weight of the compounds which boil at more than 255 ° C. (Table 4). Table 4. Simulated distillation curves of the distillate fraction% by distilled weight Boiling temperature (° C) 5% 191 10% 202 20% 222 30% 240 40% 258 50% 276 60% 293 70% 309 80% 325 90% 340 95% 347 The heavy fractions of the two previous variants A) and B) are distilled to obtain the qualities and yields of vacuum distillate and vacuum residue.

The operating conditions of the visbreaking stage coupled to a precipitation and sediment separation step according to the invention carried out on the heavy fraction have an impact on the stability of the effluents obtained. This is illustrated by the post-aging sediment contents measured in the atmospheric residues (350 ° C + cut). The performance is summarized in Table 5 below. Table 5: Summary of performances with or without precipitation, sediment separation and heavy fraction recovery Viscoréduction 46 Yes Conversion rate of compounds boiling above 540 ° C (° / 0) Precipitation (mixing with the distillate cut) Separation of sediments according to the invention Sediment content after aging (IP390 b) in the heavy fraction (350 ° C + cut) No No 0.6b According to the invention, it is possible to obtain stable effluents with a low sediment content. that a precipitation step in mixture with a distillate cut 10 according to the invention, a step of physical separation of the sediments are implemented. It is also possible to subject the effluents resulting from the steps of precipitation, physical separation of the sediments and recovery of the heavy fraction (distillation) to a fixed bed hydrotreatment stage. The operating conditions of the hydrotreatment step are shown in Table 6.

Table 6: Operating conditions of the hydrotreatment step carried out on the 350+ cuts from the visbreaking step after nassaqe at the precipitation stage, the physical separation of the sediments and distillation Hydrodemetallation catalysts (riüM) , transition and hydrodesulfurization (HDS) Cycle start temperature (° C) H2 partial pressure (MPa) VVH h-1 Snn3 h cool load / m3 fixed bed catalyst) CoMoNi on Ah. imine 370 H2 / HC entry fixed bed section excluding consumption H2 1000 (Nm3 / m3 fresh load), 3036704 22 The CoMoNi catalysts on alumina used are sold by the company Axens under the references HF858 (HDM catalyst), HM848 (catalyst of transition) and HT438 HDS catalyst). The effluents from the hydrotreating step are then separated and analyzed. The vacuum distillate fractions contain less than 0.2 wt% 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 oil bases and in particular excellent fuel oil bases.

Claims (1)

REVENDICATIONS1. 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, 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 the step a) in at least one light fraction of hydrocarbons containing fuels bases and a heavy fraction containing compounds boiling at least 350 ° C, c) a sediment precipitation step in which the heavy fraction resulting from the step separating material b) is brought into contact with a distillate cut of which at least 20% by weight has a boiling point greater than or equal to 100 ° C. for a period of less than 500 minutes at a temperature of between 25 and 350 ° C. C, e t a pressure below 20 MPa, d) a step of physical separation of the sediments of the heavy fraction resulting from step c) of precipitation to obtain said heavy fraction separated from the sediments, e) a step of recovery of a heavy fraction having a sediment content, measured according to method ISO 10307-2, less than or equal to 0.1% by weight of separating the heavy fraction resulting from step d) from the distillate cut introduced during step c ). Process according to Claim 1, comprising a step f) of fixed bed hydrotreatment carried out on at least part of the heavy fraction resulting from stage d) or e). 3. A process according to claim 1 or 2 wherein the distillate cut comprises at least 25 wt.% Having a boiling point greater than or equal to 100 ° C. 4. Method according to one of the preceding claims wherein at least 5% by weight of the distillate cut has a boiling temperature of at least 252 ° C. 5. Process according to one of the preceding claims, in which the distillate cut comes partly or even wholly from steps b) and / or d) of separation or from another refining process or from another chemical process. 6. Method according to one of the preceding claims wherein a portion of the distillate cut separated from step e) is recycled in step c) of precipitation. 7. Method according to one of the preceding claims 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 one of the preceding claims, in which a step 10 of hydrotreatment of the feed is carried out upstream of the visbreaking step a). 9. Method according to one of the preceding claims wherein the visbreaking step is performed in the presence of hydrogen. 10. Method according to one of the preceding claims wherein the step of precipitating the heavy fraction from step b) is carried out in the presence of an inert gas and / or an oxidizing gas and / or an oxidizing liquid and / or hydrogen, preferably from the separation step b). Process according to one of the preceding claims, in which the separation step d) is carried out by means of at least one separation means chosen from a filter, a separation membrane, an organic-type filter bed or inorganic, electrostatic precipitation, centrifugation system, decantation, auger withdrawal. 12. Process according to one of the preceding claims, in which the treated filler is chosen from atmospheric residues, vacuum residues from direct distillation, crude oils, crude head oils, keyed-off 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, taken alone or as a mixture. The process of claim 12 wherein the feedstock contains at least 1% C7 asphaltenes and at least 5 ppm metals. 14. Method according to one of the preceding claims wherein the heavy fractions from steps d) and / or f) are mixed with one or more fluxing bases selected from the group consisting of light cutting oils of a catalytic cracking, catalytic cracked heavy cutting oils, catalytic cracking residue, kerosene, gas oil, vacuum distillate and / or decanted oil, the distillate cut according to claims 1 to 4 to obtain a fuel oil.