FR3127228A1 - HYDROCRACKING PROCESS - Google Patents

Abstract

The invention relates to a process for the hydrocracking of a petroleum feed (1):- (a) a stage of hydrotreating the feed;- (b) a first stage of hydrocracking the hydrotreated effluent in order to obtain a first hydrocracked effluent;- (c) a stage of liquid/gas separation of the hydrocracked effluent in order to obtain a gaseous effluent and a liquid effluent;- (d) a stage of distillation of said separated liquid effluent, in order to obtain at least one unconverted heavy liquid fraction called UCO with a boiling point above 340°C;- (e1) a solid/liquid separation step of all or part of the unconverted heavy liquid fraction called UCO obtained in step (d), in order to obtain a solid residue and a liquid;- (f) a second optional step of hydrocracking a charge comprising at least a second part of the unconverted heavy liquid fraction called UCO obtained in step (d), and/or all or part of the liquid obtained in step (e1);- (e2) a step of returning at least part of the liquid obtained in the solid separation step/ liquid (e1) to the hydrotreating step (a) and/or to the first hydrocracking step (b) and/or to the second hydrocracking step (f). Figure for the abstract: Fig 3

Description

HYDROCRACKING PROCESS

The invention relates to a process for hydrocracking a petroleum feedstock. It is recalled that the hydrocracking (also referred to as hydroconversion) of heavy petroleum cuts is a key refining process which makes it possible to produce, from excess heavy feedstocks that are not very recoverable, lighter fractions such as gasoline, jet fuels and light gas oils that the refiner is looking for to adapt its production to demand. Certain hydrocracking processes also make it possible to obtain a highly purified residue which can constitute excellent bases for oils.

Hydrocracking processes are commonly used in refineries to transform hydrocarbon mixtures into easily recoverable products. These processes can be used to transform light cuts such as, for example, gasoline, into lighter cuts (also designated by the acronym LPG for "Liquefied Petroleum Gas" according to the Anglo-Saxon terminology). These processes are usually rather used to convert heavier feedstocks (such as petroleum or heavy synthetic cuts, for example gas oils from vacuum distillation or effluents from a Fischer-Tropsch unit) into gasoline or naphtha, kerosene , diesel fuel.

Certain hydrocracking processes also make it possible to obtain a highly purified residue which can constitute excellent bases for oils. One of the effluents particularly targeted by the hydrocracking process is the middle distillate (fraction which contains the gas oil cut and the kerosene cut), i.e. cuts with initial boiling points of at least 150°C and final up to before the initial boiling point of the residue, for example below 340°C, or even below 370°C.

Hydrocracking is a process that draws its flexibility, in particular, from three elements:
- the operating conditions used,
- the types of catalysts used, and
- the fact that the hydrocracking of the hydrocarbon charges can be carried out in one or two stages.

In particular, the hydrocracking of distillates under vacuum (known by the acronym DSV) makes it possible to produce light cuts (gasoil, kerosene, naphtha, etc.) that are more recoverable than DSV itself. This catalytic process does not fully transform DSV into light cuts. After fractionation, there therefore remains a more or less significant proportion of unconverted DSV fraction, called UCO (acronym for “UnConverted Oil” according to Anglo-Saxon terminology). To increase its conversion, this unconverted UCO fraction can be recycled. It can be recycled:
- at the inlet of the hydrotreating reactor, when it is planned to precede the hydrocracking of the hydrocarbon charge by a hydrotreating,
- or at the inlet of the hydrocracking reactor, in the case where it is a one-step hydrocracking process,
- or at the inlet of a second hydrocracking reactor treating the unconverted fraction at the end of the fractionation step, in the case where it is a two-step hydrocracking process.

It is known that the recycling of this UCO fraction leads to the formation of polycyclic heavy aromatic compounds called HPNA (for "Heavy PolyNuclear Aromatics" according to the Anglo-Saxon termination) during the cracking reactions, and thus to the undesirable accumulation of these compounds in the recycling loop. This accumulation leads to the degradation of the performance of the hydrocracking catalyst and/or to the fouling of the equipment.

A purge is generally installed on the recycling of said unconverted DSV UCO fraction, in particular on the line at the bottom of the fractionation, the purge flow being adjusted so as to balance the concentration of HPNAs, to control the concentration of HPNAs in the loop of recycling. Thus, the total concentration of HPNA within a recycling loop can reach values generally between 1,000 and 10,000 ppm.

The increase, in a hydrocracking process, of the conversion of a DSV feedstock into light cuts offers a definite economic advantage. This is also the reason why the unconverted fraction of DSV is recycled. On the other hand, this conversion cannot reach 100%, due to the quantity of recoverable heavy products purged at the same time as the HPNAs.

Depending on the operating conditions of the process, said purging of the heavy fraction can be between more than 0 and 5% by weight, expressed with respect to the incoming DSV feed, and preferably between 0.5% and 3% by weight. The yield of recoverable products from hydrocracking is therefore reduced by the same amount, whereas the objective of the refiner is naturally to maximize this yield.

Throughout this text, HPNA compounds are defined as polycyclic aromatic compounds which therefore comprise several aromatic rings or condensed benzene rings. They can also be called, moreover, under the acronym HPA, (for Heavy Polynuclear Aromatics according to the Anglo-Saxon terminology), or under the acronym PNA (for PolyNuclear Aromatics according to the Anglo-Saxon terminology). These compounds, formed during undesirable side reactions, are stable and very difficult to hydrocrack. Typically, HPNAs are polycyclic aromatic hydrocarbon compounds consisting of several fused benzene rings such as, for example, Coronene (compound with 24 carbons), dibenzo(e,ghi)perylene (26 carbons), naphtho[8,2 ,1,abc] coronene (30 carbons) and ovalene (32 carbons), as well as their alkylated variations. These compounds are not soluble in all proportions in UCO under the conditions of hydrocracking processes and can accumulate in solid form leading to operational problems well known to those skilled in the art (blockages/fouling of equipment, deactivations catalyst). The so-called "very heavy" HPNAs (more than 10 aromatic rings), resulting from reactions between lighter HPNAs, are presumed to be the most harmful for the hydrocracking process, due to their low solubility in UCO. They are in fact in the form of solid particles, even under high temperature conditions conventionally operated in a hydrocracker (i.e. at temperatures of at least 200°C).

Patent application WO2016/102302 describes a process for concentrating HPNAs in the unconverted fractions (residues) in order to eliminate them, and to reduce the quantity of residue purged to increase the conversion and improve the yield of recoverable products. To do this, a lateral withdrawal is set up below the feed point of the fractionation column, the withdrawn stream having a low concentration of HPNA and a large proportion of unconverted hydrocarbons in the hydrocracking section in upstream. The separation of the liquid preferably takes place by associating a stripper with the fractionation column: the stripping gas can also be injected into the lowest section of the fractionation column below the feed plate and above the point evacuation of the residue, in order to strip the distillation residue and thus to concentrate the heaviest compounds in said residue before completely purging said residue, which makes it possible to limit the loss of yield associated with the low concentration of HPNAs in the purge. In this process, no recycling step of the unconverted residue in the fractionation column is provided, and the unconverted residue is also not recycled in the hydrocracking step: It is completely purged.

Patent US9580663 describes a hydrocracking process in which part of the unconverted fraction (UCO) from the bottom of the fractionation column, is stripped against the current in a stripping column external to said fractionation column, to produce a vapor fraction at the top of the stripping column, which is then recycled to the bottom of the fractionation column, and a stripped liquid fraction concentrated in HPNA. This liquid fraction concentrated in HPNA is at least partly purged, the other part of this fraction being able to be recycled to the stripping column. This process makes it possible to concentrate the HPNAs before purging them. The high concentration of HPNA in the liquid fraction allows the removal of HPNA at a lower purge rate, which results in a higher total process conversion with an improved yield of valuable products obtained.

These different processes made it possible, at the cost of additional equipment, to reduce the fraction of UCO purged. Although more concentrated in HPNA, this fraction still contains a significant proportion of recoverable products, and the compromise between elimination rate of HPNA and loss of recoverable product therefore remains perfectible.

The aim of the invention is therefore to improve these existing solutions, in particular to find better compromises between the elimination of the HPNAs and the yield of the hydrocracking into recoverable products. It aims in particular to increase the HPNA removal rate without significantly compromising the hydrocracking yield of recoverable products, or to maintain a similar HPNA removal rate by increasing the yield of recoverable products, or to increase both removal of HPNAs and yield of valuable products.

Summary of the invention
The subject of the invention is first of all a process for the hydrocracking of a petroleum feedstock comprising at least 10% volume of compounds boiling above 340° C., said process comprising:
- (a) a step of hydrotreating the charge in the presence of hydrogen and a hydrotreating catalyst, in order to obtain a hydrotreated effluent;
- (b) a first step of hydrocracking at least a portion of the hydrotreated effluent in the presence of hydrogen and a hydrocracking catalyst in order to obtain a first hydrocracked effluent;
- (c) a step of liquid/gas separation of the hydrocracked effluent in order to obtain a separated gaseous effluent and a separated liquid effluent;
- (d) a step of distilling said separated liquid effluent, in order to obtain at least a fraction of middle distillates with a boiling point of between 150 and 370° C., an unconverted heavy liquid fraction called UCO with a boiling point greater than 340° C., optionally a gaseous fraction and optionally a gasoline fraction with a boiling point of less than 150° C.;
- (e1) a step of solid/liquid separation of all or a first part of the unconverted heavy liquid fraction called UCO obtained in step (d), in order to obtain a solid residue and a liquid;
- (f) an optional second step of hydrocracking, in the presence of hydrogen and a hydrocracking catalyst, of a charge comprising at least a second part of the unconverted heavy liquid fraction called UCO obtained in step (d), and/or all or part of the liquid obtained in step (e1) in order to obtain a second hydrocracked effluent
- (e2) a step of returning at least part of the liquid obtained in the solid/liquid separation step (e1), in particular all the liquid, to the hydrotreatment step (a) and/or to the first hydrocracking stage (b) and/or to the second hydrocracking stage (f) when it is carried out in the process.

Advantageously, step (e1) of solid/liquid separation is chosen from centrifugation and filtration. When we choose the centrifugation technique, we obtain a solid residue which is also called solid refusal or centrifugation refusal, and a liquid called centrifugation. When the filtration technique is chosen, we will speak of filtration residue for the solid obtained, and of filtrate for the liquid obtained. The terms “solid” and “liquid” are to be understood here in their known meanings in centrifugation and filtration techniques.

The invention is therefore a hydrocracking process making it possible to eliminate part of the HPNAs contained in the UCOs by solid/liquid separation, downstream of the distillation, of at least a part of these UCOs: The solid residue, very concentrated /rich in HPNA, and more particularly in very heavy HPNA (that is to say containing at least ten benzene rings), is eliminated/purged from the hydrocracking process, while the liquid, considerably depleted in HPNA, most particularly The heaviest, most damaging HPNAs can be fully recycled/returned to hydrotreating or hydrocracking. It is therefore possible both to maintain a good hydrocracking yield of recoverable products, and to eliminate more HPNA.
The invention is also very flexible in its implementation: it makes it possible to adjust the levels of conversion and elimination of the HPNAs, in particular by being able to adjust/modify the relative proportion between the UCOs obtained during the distillation, which are directly recycled to the hydrocracking (the first or the second hydrocracking, when the process comprises two hydrocracking stages), and the UCOs which will have previously been separated into solid and liquid, or even by being able to adjust/modify the way operate the solid/liquid separation (duration, centrifugation speed, filtration pressure, etc.) to adjust the relative proportion between the solid residue which will be purged and the liquid which will be recycled.

Advantageously, the method according to the invention may comprise a step (e2) of returning a third part of the unconverted heavy liquid fraction called UCO obtained in step (d) to the hydrotreatment step (a) or to the first hydrocracking stage (b): it is therefore the part of the UCO on which no solid/liquid separation has been carried out and which returns to the first hydrocracking, it is therefore not the liquid (such as the centrifugate or the filtrate) obtained by this solid/liquid separation.

This fraction of UCO not treated by the solid/liquid separation and the liquid obtained by the solid/liquid separation (centrifugeate, filtrate) can be mixed prior to their hydrocracking, or not. They can be introduced together into the hydrocracking reactor, through one or more common injection points, or be introduced through separate injection points. The choice will be made, in particular, according to the type of reactor. Heat treatment / heating can be provided on the mixture or on the liquid obtained by the solid/liquid separation alone (before mixing or in the absence of mixing) if necessary.

When the process according to the invention provides for the second hydrocracking stage (f), the second hydrocracked effluent can advantageously be returned to stage (c) of liquid/gas separation.

When the process according to the invention provides for the second hydrocracking stage (f), the process may also comprise a stage (g) of liquid/gas separation of the second hydrocracked effluent, in order to obtain a gaseous effluent, and a liquid effluent hydrocarbon which may optionally be returned to step (d) of distillation, directly or with at least one intermediate treatment of the steam stripping type.

It is therefore seen that the second hydrocracked effluent, when dealing with a hydrocracking process with two hydrocracking stages, can be separated into liquid and gas
- either with the first hydrocracked effluent, in the same separation step (c),
- or in a separate step (g), which is dedicated to it (and therefore with other equipment).

Advantageously, the separated gaseous effluent obtained in the liquid/gas separation step (c) on the hydrocracked effluent obtained in the first hydrocracking step (b) and/or obtained in the liquid/gas separation step (g ) of the hydrocracked effluent obtained in the second hydrocracking stage (f) when it is provided, is a flow of hydrogen which is returned to the hydrotreatment stage (a) and/or to the first stage ( b) hydrocracking and/or to the second hydrocracking stage (f) when it is provided.
“Hydrogen flow” is understood to mean a flow mainly, in particular essentially, consisting of hydrogen.
This hydrogen recycling thus reduces the “fresh” hydrogen consumption of the process according to the invention.

Preferably, the liquid/gas separation step (c) on the hydrocracked effluent obtained in the first hydrocracking step (b) and/or the liquid/gas separation step (g) of the second hydrocracked effluent, when it is planned, takes place by a succession of separations, in particular using a series of separator balloons operating at a pressure of at least 2 MPa, in particular between 2 and 25 MPa, and may include an optional treatment by steam stripping of the separated liquid effluent.

Preferably, in the solid/liquid separation stage (e1), the first part of the unconverted heavy liquid fraction called UCO which is separated corresponds to 0.1 to 100% by weight, in particular from 5 to 50% by weight, of preferably from 10 to 30% by weight of the heavy liquid fraction obtained in step (d).

More preferably, in the solid/liquid separation step (e1), the solid residue corresponds to 0.1 to 40% volume, in particular from 0.1 to 5% volume, preferably from 0.1 to 2% volume , of the heavy liquid fraction called UCO on which the solid/liquid separation treatment is carried out.

Preferably, the solid residue obtained in step (e1) is purged, and it is then possible to provide at least one possible treatment of this residue, for example of the drying type, to recover it in the form of solid carbon of the graphene type or carbon black. carbon. This residue is in fact generally made up of very heavy HPNA (at least 10 benzene cycles) which can thus be recovered.

Step (e1) of solid/liquid separation, in particular when it involves centrifugation, is advantageously carried out at a temperature of between 50 and 350° C., preferably between 70 and 200° C., for example between 80 and 120°C, in particular at a temperature of at most 100°C. These temperature ranges are in particular compatible with the use of centrifuges currently available for industrial applications. It may require, as detailed below, that the UCO fraction to be separated be heat-treated beforehand to reach these temperatures, this will generally involve cooling.
Step (e1), when it involves centrifugation, is advantageously carried out at a centrifugation speed of between 1,000 and 20,000 revolutions/minute, in particular between 2,000 and 10,000 revolutions/minute. Centrifugation can also advantageously be carried out at a speed expressed in centrifugation force expressed in number of G: the force applied can be chosen between 3000 G and 14000 G, in particular between 8000 G and 14000 G.

The centrifugation step (e1) of the first part of the unconverted heavy liquid fraction called UCO obtained in step (d) may comprise a cooling treatment (e') preliminary to the solid/liquid separation of said first part of the unconverted heavy liquid fraction and, optionally, a heating treatment (e'') of the liquid obtained by this separation. Indeed, as seen above, the technique chosen to operate the solid/liquid separation may require moderating the temperature of the UCO fraction to be separated, in particular for constraints, for example, related to centrifugation devices having ranges of given operating temperature, with maximum temperature thresholds not to be exceeded. But on the other hand, in order to then be able to recycle the liquid, it may be necessary to heat it afterwards, so that it reaches or approaches the temperature of the other unseparated UCO fraction which is also recycled.

Step (e1) of solid/liquid separation, in particular when it comes to filtration, is carried out on a permeable medium capable of retaining only solid particles. This filtering medium is characterized by a pore size which can vary from 0.5 μm to 80 μm, preferably from 1 μm to 5 μm.

To drive the fluid through the filter medium, a driving force equal to or greater than the pressure drop must be applied. This force can come from a pressure applied to the suspension upstream of the filter, from a vacuum effect applied downstream from the filter, from centrifugal force or from the force of gravity. The key is to have a pressure differential across the filter allowing the fluid to flow.

In the case of filtration of HPNAs present in _UCOs , the main purpose is to clarify the liquid by removing solid particles. The concentration of HPNA particles is generally less than 1% by weight, and their size varies from 1 μm to 80 μm.

Surface filtration is the most appropriate. In this type of filtration, the particle diameter is greater than the pore diameter, and the particles are retained due to their size. Examples of this type of filter that can be used for the filtration of HPNA are: filter cartridges, micro-sieves, fabric filters, pocket filters, and more generally any filtering surface with a pore size of for example at most or equal to 0.5 µm to retain particles larger than 0.5 to 80 µm.

The driving force can come from the pressure applied to the fluid, from the centrifugal force or from the gravitational force. The force applied must be able to overcome a pressure drop in the filter that can vary between 75 kPa and 800 kPa depending on the model chosen.

According to a first embodiment, the solid/liquid separation step (e1) comprises the preliminary cooling treatment (e') of said first part of the unconverted heavy liquid fraction and the heating treatment (e'') of the liquid obtained, and this cooling and this heating are carried out by heat transfer, in particular by a feed-effluent type exchanger, from the first part of the unconverted heavy liquid fraction to the liquid separated in step e1) (centrifuge, filtrate in particular).

The invention also relates to a hydrocracking installation implementing the process described above.

The invention also relates to an installation for the hydrocracking of a petroleum feedstock (1) comprising at least 10% volume of compounds boiling above 340° C., said installation comprising:
- (a) a hydrotreating section of the charge comprising at least one reactor (R1) in the presence of hydrogen and a hydrotreating catalyst, in order to obtain a hydrotreated effluent;
- (b) a first section for hydrocracking at least part of the hydrotreated effluent comprising at least one reactor (R2) in the presence of hydrogen and a hydrocracking catalyst in order to obtain a first hydrocracked effluent ;
- (c) a section for the liquid/gas separation of the hydrocracked effluent, comprising in particular a series of separator drums at pressure between 2 and 25 MPa, in order to obtain a separated gaseous effluent and a separated liquid effluent;
- (d) a section for distilling said separated liquid effluent, comprising at least one distillation column, in order to obtain at least a fraction of middle distillates with a boiling point of between 150 and 370°C, a heavy liquid fraction not converted so-called UCO with a boiling point above 340° C., optionally a gaseous fraction and optionally a gasoline fraction with a boiling point below 150° C.;
- (e1) a solid/liquid separation section for all or a first part of the unconverted heavy liquid fraction called UCO obtained in step (d), comprising in particular at least one centrifuge device and/or one device filtration, in order to obtain a solid residue and a liquid;
- (f) a second optional hydrocracking section, comprising at least one reactor (R3) in the presence of hydrogen and a hydrocracking catalyst, of a charge comprising at least a second part of the heavy liquid fraction not converted so-called UCO obtained in step (d), in order to obtain a second hydrocracked effluent;
- (e2) a section for returning at least part of the liquid obtained in the solid/liquid separation step (e1), in particular all the liquid, to the hydrotreatment section (a), and/or to the first hydrocracking section (b) and/or to the second hydrocracking section (f) when it is operated in the process, said return section comprising conduit-type fluidic connections between the solid/liquid separation section (e1 ) and one and/or the other of the hydrocracking (b, f) and/or hydrotreating (a) sections.

The invention can thus have recourse to a centrifugation device (a centrifuge), which can be positioned downstream of the distillation section (also called fractionation) of the products resulting from the hydrocracking process, or to a filtration device which can also be positioned downstream of the distillation section.

This installation may comprise at least one charge-effluent type heat exchanger to ensure heat transfer from the first part of the unconverted heavy liquid fraction obtained in step (d) to the centrifugate obtained in step (e1) and / or at least one mixer to mix the gaseous fraction and/or the gasoline fraction with a boiling point below 150° C., previously cooled, with the said first part of the unconverted heavy liquid fraction obtained in step ( d).

List of Figures

There represents a block diagram of a hydrocracking process according to the prior art, with a hydrocracking step.

There represents a block diagram of a hydrocracking process according to the prior art, with two hydrocracking stages.

There represents a block diagram of a hydrocracking process according to a first embodiment of the invention, with a single hydrocracking step.

There represents a variant according to the invention of the diagram of the , with a single hydrocracking step.

There represents a block diagram of a hydrocracking process according to a second embodiment of the invention, with two hydrocracking stages.

There represents a variant according to the invention of the diagram of the , with two hydrocracking steps.

All of these figures are very schematic, do not necessarily respect the scale or the spatial distribution of the different devices represented. Identical references from one figure to another correspond to the same compounds/lines/devices.

Description of figures

There represents a conventional one-stage hydrocracking process:
- charge 1 as well as hydrogen supply a hydrotreatment section a),
- the hydrotreated effluent 2 as well as hydrogen supply a hydrocracking section b)
- the hydrocracked effluent 3 feeds a gas/liquid separation section c), at the outlet a gaseous effluent 4 and a liquid effluent 5 are obtained
- the liquid effluent 5 feeds a distillation section d) (also called the fractionation section), at the outlet one obtains, from the top to the bottom of the distillation column, a gaseous effluent 11 of LP Off-gas (Anglo-Saxon terminology designating hydrocarbon compounds from C1 to C4-C5, therefore lighter than naphtha, which comprises hydrocarbon compounds from C5-C6 and more) a naphtha effluent 6, a kerozene effluent 7, a diesel effluent 8 and an effluent 9 of UCO withdrawn at the bottom of the column.
The HPNA-rich effluent 9 is divided into a purge stream 10 (removed from the process) and a stream 9' and/or 9'' which is recycled respectively at the inlet of the hydrotreatment section a) or at the inlet of the hydrocracking section b).

There represents a conventional hydrocracking process with two hydrocracking stages: only the characteristics which differ from the . The effluent 9, the UCO, at the outlet of the distillation section d) is shared between the purge stream 10 and a stream 12 which feeds a second hydrocracking section f). From this second hydrocracking section emerges a hydrocracked effluent 13 which is returned to the inlet of the separation section (c).

There represents a hydrocracking process according to the invention in a hydrocracking step. Only the differences from the : here, the UCO effluent 9 feeds a solid/liquid separation section, for example by centrifugation or filtration (e1), from which emerges, on the one hand, a solid residue 14 (solid rejection in the case of centrifugation, filtration residue in the case of filtration) which leaves the process, on the other hand a liquid 15 (centrifugate in the case of centrifugation, filtrate in the case of filtration) which is returned to the inlet hydrotreating section (a) or hydrocracking section inlet (b), as shown by the dotted arrows in the figure, references 15'' and 15' respectively.

There is a variant according to the invention of the : here the UCO 9 effluent is divided into a stream 16 and a stream 17: the stream 17 feeds the solid/liquid separation section (e1), from which it emerges, as in the previous figure, of a on the one hand a solid residue 14 which leaves the process, on the other hand a liquid 15. The liquid 15 is here mixed with the stream 16, to form a stream 18 which is returned either to the inlet of the hydrotreatment section (a) ( stream 18''), or at the inlet of the hydrocracking section (b) (stream 18').

In fact, the invention provides for numerous variants with regard to the processing of the UCO stream 9 leaving the fractionation section (d), including in particular the following three:
- Either all of the effluent 9 is sent to the solid/liquid separation section (e1) ( ),
- either only part of the effluent 9 is sent to the solid/liquid separation section ( ), the remainder of the effluent being able to be returned directly to the inlet of the hydrotreating and/or hydrocracking section (or of the second hydrocracking section when the process comprises two hydrocracking sections, as detailed in the following figures),
- either part of the effluent 9 is purged, another part is treated in the solid/liquid separation section (e1), and yet another part (the rest of the effluent) is returned to the inlet of the section d hydrotreating and/or hydrocracking (or of the second hydrocracking section when the process comprises two hydrocracking sections, as detailed in the following figures).

The invention also provides numerous variants with regard to the treatment of the flow of liquid leaving the solid/liquid separation section (e1), including in particular the following:
- the liquid is returned directly to the inlet of the hydrotreating section (a), to the inlet of the hydrocracking section (b) ( ), or at the inlet of the second hydrocracking section when the process comprises two hydrocracking sections
- the liquid 15 is mixed with part of the UCO effluent 9, before returning the mixture to the inlet of the hydrotreating (a) or hydrocracking (b) section ( ), or at the inlet of the second hydrocracking section when the process comprises two hydrocracking sections;
- only part of the liquid is used according to one or other of the preceding variants, another part being exploited/upgraded outside the hydrocracking process of the invention.

The different processing variants of UCO 9 and Liquid 15 can be combined.

There represents a hydrocracking process according to the invention with two hydrocracking stages. Only the differences from the : at the output of step (e1) of solid/liquid separation, a solid residue 14 which leaves the process and a liquid 15 which feeds a second hydrocracking section (f) are recovered. The effluent 19 at the outlet of this second hydrocracking section is returned to the inlet of the liquid/gas separation step (c).

There is a variant of the hydrocracking process according to the invention with two hydrocracking stages according to the : a part 17 of the UCO effluent 9 is sent to the solid/liquid separation section (e1), another part 20 is mixed with the liquid 15 leaving the solid/liquid separation section (e1). The mixture 21 of these two streams feeds the second hydrocracking section (f). At the outlet of the second hydrocracking section (f), the effluent 19 is returned as previously to the inlet of the liquid/gas separation section (c).

Claims (15)

Process for hydrocracking a petroleum feedstock (1) comprising at least 10% by volume of compounds boiling above 340°C, said process comprising:
- (a) a step of hydrotreating the charge in the presence of hydrogen and a hydrotreating catalyst, in order to obtain a hydrotreated effluent;
- (b) a first step of hydrocracking at least a portion of the hydrotreated effluent in the presence of hydrogen and a hydrocracking catalyst in order to obtain a first hydrocracked effluent;
- (c) a step of liquid/gas separation of the hydrocracked effluent in order to obtain a separated gaseous effluent and a separated liquid effluent;
- (d) a step of distilling said separated liquid effluent, in order to obtain at least a fraction of middle distillates with a boiling point of between 150 and 370° C., an unconverted heavy liquid fraction called UCO with a boiling point greater than 340° C., optionally a gaseous fraction and optionally a gasoline fraction with a boiling point of less than 150° C.;
- (e1) a step of solid/liquid separation of all or a first part of the unconverted heavy liquid fraction called UCO obtained in step (d), in order to obtain a solid residue and a liquid;
- (f) an optional second step of hydrocracking, in the presence of hydrogen and a hydrocracking catalyst, of a charge comprising at least a second part of the unconverted heavy liquid fraction called UCO obtained in step (d), and/or all or part of the liquid obtained in step (e1) in order to obtain a second hydrocracked effluent
- (e2) a step of returning at least part of the liquid obtained in the solid/liquid separation step (e1), in particular all the liquid, to the hydrotreatment step (a) and/or to the first hydrocracking stage (b) and/or to the second hydrocracking stage (f) when it is carried out in the process. Hydrocracking process according to the preceding claim, characterized in that step (e1) of solid/liquid separation is chosen from centrifugation and filtration. Hydrocracking process according to the preceding claim, characterized in that it comprises a step (e2) of returning a third part of the unconverted heavy liquid fraction called UCO obtained in step (d) to step d hydrotreating (a) or to the first hydrocracking stage (b). Hydrocracking process according to one of the preceding claims, characterized in that it provides for the second hydrocracking stage (f), and in that the second hydrocracked effluent is returned to stage (c) of liquid/ gas. Hydrocracking process according to one of Claims 1 to 3, characterized in that it provides for the second hydrocracking stage (f), and also a stage (g) of liquid/gas separation of the second hydrocracked effluent, in order to obtaining a gaseous effluent, and a liquid hydrocarbon effluent which can optionally be returned to step (d) of distillation, directly or with at least one intermediate treatment of the steam stripping type. Hydrocracking process according to one of the preceding claims, characterized in that the separated gaseous effluent obtained in the liquid/gas separation stage (c) on the hydrocracked effluent obtained in the first hydrocracking stage (b) and/or obtained at the liquid/gas separation stage (g) of the hydrocracked effluent obtained at the second hydrocracking stage (f) when it is provided, is a flow of hydrogen which is returned to the stage (a) of hydrotreating and/or to the first stage (b) of hydrocracking and/or to the second stage of hydrocracking (f) when it is provided Hydrocracking process according to one of the preceding claims, characterized in that the liquid/gas separation step (c) on the hydrocracked effluent obtained in the first hydrocracking step (b) and/or the step of liquid/gas separation (g) of the second hydrocracked effluent when it is planned takes place by a succession of separations, in particular using a series of separator drums operating at a pressure of at least 2 MPa, in particular between 2 and 25 MPa, and includes an optional treatment by steam stripping of the separated liquid effluent. Hydrocracking process according to one of the preceding claims, characterized in that the solid residue obtained in step (e1) is purged, with optional treatment of the drying type, in order to recover it in the form of solid carbon of the graphene type or black of carbon. Hydrocracking process according to one of the preceding claims, characterized in that, in the solid/liquid separation stage (e1), the first part of the unconverted heavy liquid fraction called UCO which is separated corresponds to 0.1 at 100% by weight, in particular from 5 to 50% by weight, preferably from 10 to 30% by weight of the heavy liquid fraction obtained in step (d). Hydrocracking process according to one of the preceding claims, characterized in that, in the solid/liquid separation stage (e1), the solid residue corresponds to 0.1 to 40% volume, in particular from 0.1 to 5 % volume, preferably from 0.1 to 2% volume, of the heavy liquid fraction called UCO on which the solid/liquid separation treatment is carried out. Hydrocracking process according to one of the preceding claims, characterized in that the solid/liquid separation step (e1) of the first part of the unconverted heavy liquid fraction called UCO obtained in step (d) comprises a cooling treatment (e') preliminary to the separation of said first part of the unconverted heavy liquid fraction and, optionally, a heating treatment (e'') of the liquid obtained. Hydrocracking process according to Claim 11, characterized in that in stage (d) at least one fraction of middle distillates with a boiling point of between 150 and 370°C, an unconverted heavy liquid fraction called UCO with a boiling point above 340°C, and a gaseous fraction and/or a gasoline fraction with a boiling point below 150°C, in particular previously cooled, and in that the preliminary cooling treatment (e') of said first part of the unconverted heavy liquid fraction from the solid/liquid separation stage (e1) is carried out by mixing the gaseous fraction and/or the gasoline fraction with a boiling point below 150°C with said first part of the unconverted heavy liquid fraction. Installation for hydrocracking a petroleum feedstock (1) comprising at least 10% volume of compounds boiling above 340°C, said installation comprising:
- (a) a hydrotreating section of the charge comprising at least one reactor (R1) in the presence of hydrogen and a hydrotreating catalyst, in order to obtain a hydrotreated effluent;
- (b) a first section for hydrocracking at least part of the hydrotreated effluent comprising at least one reactor (R2) in the presence of hydrogen and a hydrocracking catalyst in order to obtain a first hydrocracked effluent ;
- (c) a section for the liquid/gas separation of the hydrocracked effluent, comprising in particular a series of separator drums at pressure between 2 and 25 MPa, in order to obtain a separated gaseous effluent and a separated liquid effluent;
- (d) a section for distilling said separated liquid effluent, comprising at least one distillation column, in order to obtain at least a fraction of middle distillates with a boiling point of between 150 and 370°C, a heavy liquid fraction not converted so-called UCO with a boiling point above 340° C., optionally a gaseous fraction and optionally a gasoline fraction with a boiling point below 150° C.;
- (e1) a solid/liquid separation section for all or a first part of the unconverted heavy liquid fraction called UCO obtained in step (d), comprising at least one separation device, in order to obtain a solid residue and a liquid;
- (f) a second optional hydrocracking section, comprising at least one reactor (R3) in the presence of hydrogen and a hydrocracking catalyst, of a charge comprising at least a second part of the heavy liquid fraction not converted so-called UCO obtained in step (d), in order to obtain a second hydrocracked effluent;
- (e2) a section for returning at least part of the liquid obtained in the solid/liquid separation step (e1), in particular all the liquid, to the hydrotreatment section (a), and/or to the first hydrocracking section (b) and/or to the second hydrocracking section (f) when it is operated in the process, said return section comprising conduit-type fluidic connections between the solid/liquid separation section (e1 ) and one and/or the other of the hydrocracking (b, f) and/or hydrotreating (a) sections. Installation according to the preceding claim, characterized in that the solid/liquid separation section (e1) comprises at least one device chosen from among a centrifugation device and/or a filtration device. Installation according to claim 13 or 14, characterized in that it comprises at least one charge-effluent type heat exchanger to ensure heat transfer from the first part of the unconverted heavy liquid fraction obtained in stage (d) to the liquid obtained in step (e1) and/or at least one mixer to ensure the mixing of the gaseous fraction and/or of the gasoline fraction with a boiling point below 150° C., in particular previously cooled, with the said first part of the unconverted heavy liquid fraction obtained in step (d).