Hydroconversion process of heavy charges including the treatment of slurry streams and the relevant plant

Abstract

Method of hydroconversion of Heavy charges as feedstock comprising the steps of Hydrotreating a heavy charge in a slurry reactor in the presence of hydrogen and a dispersed hydrotreating catalyst deriving from said Molybdenum-based Precursor of catalyst to obtain an effluent (1) of hydroconversion reaction; Submitting the effluent (1) to gas-liquid separation to separate distillates in form of Vacuum Gas Oil (VGO), Heavy Vacuum Gas Oil (HVGO), Light Vacuum Gas Oil (LVGO), Atmospheric Gas Oil (AGO) fractions from at least one slurry phase comprising asphaltenes, unconverted feedstock, catalyst and solids formed during the hydroconversion reaction; characterized in that said method of hydroconversion further includes a primary solid-liquid separation to treat said at least one slurry phase separated from one or more distillates, said primary solid-liquid separation being selected from - cross flow filtration (CFF) without solvent, - diafiltration with a solvent, or - cross flow filtration (CFF) without solvent followed by a subsequent diafiltration with a solvent.

Description

[0001] HYDROCONVERSION PROCESS OF HEAVY CHARGES INCLUDING THE

[0002] TREATMENT OF SLURRY STREAMS AND THE RELEVANT PLANT

[0003] DESCRIPTION

[0004] The present invention relates to a method for obtaining an improved slurry hydroconversion reaction of heavy charge or feedstock, e.g. mainly Heavy oil, carried out in slurry reactor in the presence of a slurry of hydroconversion unsupported catalyst deriving from a liquid molybdenum-based precursor .

[0005] Particularly, the present invention relates to such a slurry hydroconversion method (and the relevant plant) based on the Eni Slurry Technology (EST) in which it is further provided advantageously the application of a specific filtration method (and the relevant device (s) ) to the purge stream or to a slurry stream (or mixture of slurry streams) exiting from the bottom of one or more vapour-liquid separator devices to obtain valuable products other than metals, said method allowing to improve, at least in some configurations, the conversion of the heavy oil charge by reducing the percentage of the purge stream with respect to the fresh feedstock thanks to fact that a separation of high quantity of oil from the solids contained in a slurry stream or purge is provided. The recovered oil from the slurry stream / purge can be recycled to the hydro-conversion reactor or can be valorized as such as a product. More particularly, the present invention relates to such an improved hydroconversion method as above wherein the specific filtration process is selected from crossflow filtration (CFF) , diaf iltrat ion with solvent or combination thereof .

[0006] Still more particularly, the present invention relates to such an improved hydroconversion method (and the relevant plant) of heavy feedstocks which may, additionally or alternatively, valorize products other than the catalyst recovery, e.g. HSFO (high sulphur fuel oil) , fuel oil, depending on heavy feedstocks: this entails more flexibility in terms of fresh feedstock and in terms of valuable coproducts, not only in terms of spent catalyst.

[0007] BACKGROUND of THE INVENTION

[0008] The process of hydroconversion of a heavy oil feedstock according to the EST technology (hereinafter identified also with the term "EST process" ) is a slurry process characterized by a slurry reactor, e.g. a bubble reactor, and by the presence of a unsupported catalyst uniformly dispersed in the hydrocarbon oil phase of the feedstock: the unsupported catalyst derives from an oleo-soluble liquid Molybdenum-based precursor which is generally fed to the reactor and the particles of the unsupported catalyst are formed "in situ" with very small average dimensions, e.g. 5-

[0009] 40 micron. The EST process is effected in two stages wherein the first stage provides the hydrotreating of the Heavy oil feedstock in the presence of hydrogen and catalyst to break the asphaltenic structures of the heavy oil having high molecular weight in order to convert part of them into distillates (second stage) with lower molecular weight: at the outlet of the hydroconversion reactor the effluent is undergone to different steps of vapour-liquid separation to obtain many different light products (distillates) . The EST process also provides the step of separating the spent catalyst from the purge stream by sedimentation of said purge in order to recover metals.

[0010] In the EST process, the purge is a portion of the bottom of vacuum distillation tower (i.e. residue of distillation) and generally contains 5-8% of solids including spent catalyst: the purge stream is provided to avoid the accumulation of solids in the equipment, given that the EST process provides to recycle the residue of distillation containing solids to the hydroconversion reactor in order to hydrotreat the unconverted heavy oil still contained in the bottom stream of vacuum distillation tower and to combine it with fresh catalyst and fresh feedstock as make-up.

[0011] The purge stream of the EST process ranges conventionally from 6% to 8% with respect to the fresh feedstock, it is rich in metal sulfides and contains unconverted heavy oil including asphaltenes, carbonaceous residues and catalyst in dispersed phase. Said percentage of exiting purge stream with respect to the fresh feed entails that the conversion into products varies from 92% to 94% with respect to the fresh feedstock (100%-%purge) .

[0012] In the EST process the purge is treated by static decantation to recover a clarified stream to be recycled to the reactor in order to convert possible unconverted heavy charge still remaining in the clarified stream.

[0013] Accordingly, if in the conventional EST process it is desired to increase percentage of the exiting purge stream, e.g. from 6% to 10%, to recover by decantation increased amounts of clarified stream, the percentage of conversion as defined above decrease.

[0014] Thus, there is a need in the field of the slurry hydroconversion of Heavy oil feedstock using the EST process to at least increase the amount of clarified stream that can be recycled without increasing the conventional percentage of purge stream from distillation residue in order to avoid the decrease of conversion.

[0015] In the hydroconversion processes of prior art which are different from EST technology in view of the different catalyst, different hydroconversion reactor and different configurations of process and plant, it is provided the recovery of the spent supported catalyst by using primary separation systems, e.g. a hydrocyclone, in association with cross-flow filter (CFF) , thus requesting a complex and expensive configuration for recovering catalyst from a slurry stream.

[0016] For example, U.S. 2017 / 0050177 Al discloses a slurry hydroconversion process of Heavy oil feedstock wherein the spent supported bimetallic catalyst is recovered from the bottom stream of the gas-liquid separator: the catalyst recovery is effected in a primary separation device defined by a hydrocyclone to obtain a catalyst-rich stream which is partially recycled to the slurry reactor and partially purged whereas the lean, clarified slurry stream obtained from the hydrocyclone is sent to a secondary loop including a crossflow filtration system to remove submicron catalyst particles. The crossflow filtration (usually limited to a solids content of max 25-35%) produces a liquid product which is sent to the battery limit. The lean stream entering the CFF is a lean catalyst slurry, i.e. the content of solid catalyst is low since catalyst particles are mainly recovered by the hydrocyclone through the catalyst-rich stream and purge .

[0017] US 10, 414, 991 B2 discloses a process to recover catalyst particles larger than 2 micron from slurry hydroprocessing effluent, wherein a cyclone or other separation drums are applied to a slurry stream followed by a cross-flow filtration in order to recover at least 95% wt . of the spent catalyst in form of particles larger than 2 microns from slurry effluent.

[0018] US2009 / 0159505A1 discloses a system to recover valuable metals from spent catalyst by separating spent catalyst particles having an average particle size of at least 1 micron from heavy oil using a deoiling process which includes a membrane filtration, e.g. cross-flow filtration (CFF) , with solvent e.g. toluene, which is required to replace the heavy oil in the slurry fed to the filtration unit and to have an easier separation with respect to conventional filtration since unsupported fine catalyst of slurry catalyst, e.g. particles having dimensions about 0, 1 micron, may cause plugging or fouling of the filter. The lean stream obtained from membrane filtration and containing toluene is recycled to the filtration unit to be used as solvent for the feed stream entering the earlier filtration unit. The presence of toluene in the lean stream obtained from diaf iltrat ion would be problematic if the lean stream were recycled to a hydroconversion slurry reactor of EST process which operates at very high temperatures.

[0019] US 8, 080, 154 B2 discloses a system for separating heavy oil from slurry spent catalyst in heavy oil in order to reuse the recovered catalyst as secondary source of metals, wherein hydroprocessing slurry catalyst containing about 12% of solids in unconverted heavy oil is processed by eight stages of CFF units to concentrate the solids. The feed to CFF unit in each stage is diluted with an amount of toluene (i.e. a light hydrocarbon solvent) equal to the original feed slurry. The lean stream obtained from CFF and containing toluene is recycled to the filtration unit to be used as solvent for the feed stream entering the earlier filtration unit. The heavy oil is recovered together with the solvent, e.g. toluene, as filtrate stream (permeate) : the presence of toluene in the filtrate stream prevents the filtrate stream to be recycled as such to the hydro-conversion slurry reactor of EST process which operates at very high temperatures.

[0020] Thus, in the state of art of hydroconversion processes of heavy oil different from EST process, the filtration has only the objective of recovery spent catalyst to regenerate it or to recover precious metals.

[0021] In contrast, in the EST process the purge is treated by static decantation to recover a clarified stream to be recycled to the reactor.

[0022] However, the use of decantation step in the EST process has the drawback to entails a high degree of deposits on the walls of decantation apparatus since the time of separation is prolonged, thus requesting frequently stops to remove the deposits .

[0023] US 8, 147, 675 B2 describing the EST process provides the use of two hydroconversion reactors operating at different pressure and temperature and contemplates a generic filtration step as alternative to the deasphalting step to separate solids from vacuum tower bottom: the filtration is suggested to be performed by using diluent solvent.

[0024] It could be desirable to have a hydroconversion process of heavy feedstock mainly including Heavy oil according to EST process which valorizes streams other than the catalyst recovery, e.g. recovered oil streams, as a valuable products as such in order to achieve more flexibility in the hydroconversion EST process and plant.

[0025] The Applicants have found a simple and economic method of hydroconversion of Heavy oil feedstock which allows to valorize streams other than the catalyst recovery as a valuable products depending on the type of feedstock in order to achieve more flexibility in the EST process in terms of fresh feedstock and in terms of valuable co-products, not only in terms of spent catalyst.

[0026] In particular, the Applicants have found a simple and economic method of hydro-conversion of Heavy oil feedstock carried out in accordance with the EST process which allows to recover from a slurry stream a clarified stream containing no solids that can be sent to the slurry stripper so that the downstream vacuum tower of distillation does not become foul and no purge is needed from vacuum distillation tower. The method of the present invention provides a hydroconversion reaction of heavy charges according to EST process which further comprises a primary separation of one or more slurry streams from the bottom of vapour-liquid separators devices, including the purge stream, said primary separation being formed by a Cross Flow Filtration (CFF) , a diaf iltrat ion or a Cross Flow Filtration (CFF) followed by a diaf iltrat ion, wherein said primary separation unit is fed with said slurry stream (s) to separate the slurry stream (s) into a solid-rich stream and a lean clean stream, wherein at least a portion of said lean stream and / or of said solidrich stream is recycled to the hydroconversion reactor.

[0027] "Cross-flow filtration" (or crossflow filtration or tangential flow filtration (TFF) ) refers to a filtration technique in which the feed stream flows (parallel or tangentially) along the surface of a membrane and the filtrate flows across said membrane.

[0028] In cross-flow filtration, typically only the material which is smaller than the membrane pore size passes through (across) the membrane as permeate or filtrate, and everything else is retained on the feed side of the membrane as retentate or concentrate.

[0029] The diaf iltrat ion is a particular form of "cross-flow filtration" and it is generally performed in two stages: a first stage of concentration and a second stage wherein a volume of solvent is added to replace the volume of filtrate.

[0030] In the present invention, the cross-flow filtration technique, diaf iltration or combination thereof is applied on different slurry stream (s) of hydro-conversion reaction of heavy charge of EST process including the purge from distillate residue so that it is achieved more flexibility in terms of fresh feedstock which can be processed in the hydroconversion process while obtaining improved conversion as defined above and / or valuable products other than metals.

[0031] In fact, one of the advantage of the present method and the relevant plant is the possibility of processing through the EST process, feedstocks also containing high quantity of solids or high amounts of components which can became solids after hydroconversion in the EST process.

[0032] Another advantage of the method of the present invention is that it allows to valorize the stream of concentrate solids (i.e. solid-rich stream) since the concentrate solids open the possibility to recovery metals from that stream.

[0033] By using the cross-flow filtration, diaf iltration or combination thereof it is indeed possible to separate a solid-rich stream from a clarified one. Solids can be initially present in the fresh feedstock or formed as a catalyst, as a by-product or as a co-product during the hydroconversion process.

[0034] It is an objective of the present invention to provide a method of hydroconversion of Heavy charges as feedstock comprising the following steps:

[0035] (A) Feeding a Molybdenum-based Precursor of a Molybdenum- based hydrogenation catalyst to a slurry reactor;

[0036] (B) Feeding a heavy charge comprising asphaltenes to said slurry reactor;

[0037] (C) Hydrotreating the heavy charge in said slurry reactor in the presence of hydrogen and a dispersed hydrotreating unsupported catalyst deriving from said Molybdenum-based Precursor of catalyst to obtain an effluent (1) of hydroconversion reaction;

[0038] (D) Submitting the effluent (1) to gas-liquid separation to separate distillates (fractions) in form of Vacuum Gas Oil (VGO) , Heavy Vacuum Gas Oil (HVGO) , Light Vacuum Gas Oil (LVGO) , Atmospheric Gas Oil (AGO) from at least one slurry phase comprising asphaltenes, said feedstock in unconverted form, catalyst and solids formed during the hydroconversion reaction; said gas-liquid separation being carried out in a separation unit comprising a Hot high pressure separator (HHPS) , a Hot low pressure separator (HLPS) , a slurry stripper (stripping column) and distillation vacuum tower in liquid communication with each other, said gas-liquid separation unit optionally including a Low pressure Slurry Purge Separator (LPSPS) in slurry communication with said slurry reactor characterized in that said method of hydroconversion further comprises a primary solid-liquid separation step to treat

[0039] - a purge (10) , said purge being a part of a bottom stream

[0040] (9) from said distillation vacuum tower; or

[0041] - said at least one slurry phase previously separated from one or more distillates, said primary solid-liquid separation being selected from

[0042] - cross flow filtration (CFF) without solvent;

[0043] - diaf iltrat ion with a solvent; and

[0044] - cross flow filtration (CFF) without solvent followed by a subsequent diaf iltrat ion with a solvent, said at least one slurry phase previously separated from one or more of said distillates or a portion (30; 31) of said at least one slurry phase being then submitted to said primary solid-liquid separation step to separate a solidrich stream (12; 14; 18; 34; 42; 44) , optionally including said solvent, from a solid-free lean stream (13; 17; 19; 33; 41; 43) , optionally including said solvent; said at least one slurry phase submitted to said primary solid-liquid separation being selected from

[0045] - a bottom stream (6) from said Low pressure Slurry Purge Separator (LPSPS) , if present;

[0046] - a bottom stream (7) from said Hot low pressure separator (HLPS) ;

[0047] - a portion (30; 31) of a bottom stream (7; 8) from said

[0048] Hot low pressure separator (HPLS) or said slurry stripper;

[0049] - a combined stream (32) of portions (30; 31) of bottom streams from said Hot low pressure separator (HPLS) and said slurry stripper.

[0050] With the term " solid- free lean liquid / stream" it is herein intended to identify a liquid or a liquid stream containing negligible amounts of solids, generally lower than 1000 ppm, preferably lower than 100 ppm.

[0051] With the term "solid-rich stream" it is herein intended to identify a liquid, slurry or solid stream that contains quite all the amounts of solids (e.g. kg / h) contained in the slurry stream entering the primary solid-liquid separation unit provided in the present method of the invention.

[0052] The solid-free lean liquid / stream obtained after the primary separation step, hereinafter identified also with the terms "clarified permeate" , may be then:

[0053] - recycled back to the hydroconversion reactor to improve said conversion of the fresh feedstock; or

[0054] - sent downstream to distillation section such as slurry stripper or distillation column (vacuum tower) ; or valorized as fuel oil product or as High Sulphur Fuel oil (HSFO) product; or

[0055] - further upgraded to remove sulfur to produce very low sulfur fuel oil (VLSFO) ;

[0056] - a combination thereof; or

[0057] - sent to downstream applicat ion / treatment if solvent needs to be removed.

[0058] The obtained solid-rich stream may be then

[0059] - partially purged and partially recycled to the reactor; or

[0060] - totally purged; or

[0061] - sent to downstream application if solvent is further removed .

[0062] In the present disclosure, the term "heavy charges" means to identify different kinds of feedstocks such as heavy crude oils, distillation residues, heavy oils coming from catalytic treatment, for example heavy cycle oils from catalytic cracking treatment, thermal tars (coming for example from vis-breaking or similar thermal processes) , tars from oil sands, various kinds of coals and any other high-boiling charge of a hydrocarbon origin generally known in the art as "black oils" .

[0063] In the present disclosure, " slurry" , "slurry phase" means a mixture of liquid and solid.

[0064] In the present disclosure, the term "purge" means slurryphase organic streams which contain an amount of hydrocarbons having a boiling point greater than or equal to 540°C, greater than 65% by weight, an amount of asphaltenes greater than or equal to 20% by weight and characterized by the presence of solids contents greater than or equal to 4% by weight, the remainder being hydrocarbons having a boiling point comprised between 350°C and 500°C.

[0065] Purge solids contain carbonaceous residues and metal compounds which may contain sulphides of transition metals, such as for example molybdenum, iron, nickel and vanadium, and having sub-millimeter sizes.

[0066] In the present disclosure, the term "solid" means the fraction that is not soluble in tetrahydrofuran, said fraction being indicated in this text by the acronym THF-i (THF insolubles) : in addition to the catalyst, in the slurry stream there are others kind of solids that also depend on the nature of feedstock; usually solids are formed during the hydroconversion process and they are nickel, vanadium and iron sulphides, and carbonaceous particles. If in the heavy oil feed there is some plastic material, it partially remains as a solid if it is unconverted. In addition, plastic materials have some solid fillers in the formulation improving specific properties and making the plastic product cheaper. All these solid particles are insoluble in tetrahydrofuran (THF Insoluble or THF-i) so it is possible to measure their concentration measuring the amount of THF- In the present disclosure, the term "asphaltenes" means the organic fraction that is soluble in tetrahydrofuran but insoluble in n-pentane. Asphaltenes are classified based on their insolubility in n-paraffins (typically having from 5 to 7 carbon atoms C5-C7) . Such compounds are generally constituted by nuclei of aromatic polycondensates variously branched and joined together through linear chains. Such compounds may contain heteroatoms (S, N) therein which give them their polar nature.

[0067] For the purposes of the present discussion the terms " comprising" , "including" also comprise the term "consisting of" or "consisting essentially of" .

[0068] For the purposes of this disclosure the definitions of the ranges always comprise the ends unless otherwise specified .

[0069] In the following description, the terms "sent", "transferred" and the like are to be intended effected via pumps or other fluid handling means apt to move / transf er fluids including slurry.

[0070] The slurry stream entering the reactor in the EST process and in the present invention generally contains 5-12% by weight of solids, preferably 5-8%: the solids contained in said slurry stream entering the reactor includes the particles of the catalyst having average dimension of 5-40 micron .

[0071] The above concentration of solids and dimensions of particles size can slightly be different for the various slurry streams exiting from the bottom of the gas-liquid separation apparatuses provided to carry out the EST process: in any case the use of primary solid-liquid separation by means of the specific filtration units as described above allows to concentrate the solids of a slurry stream or purge up to 20-25% in a first outlet stream while obtaining a second stream containing no solids as will be explained in detail here below.

[0072] In particular the primary solid-liquid separation of the present invention employs at least a filter membrane for removing at least 50%, preferably 75%, of the heavy oil from the solids, both contained in a purge stream or in a slurry stream and separating the feed stream into: a) a filtrate stream comprising the removed heavy oil; and b) a retentate stream containing solids.

[0073] The catalyst used in the method of the present invention is an unsupported hydrogenation metal catalyst containing Molybdenum as active metal: it is generated from an oleo- soluble liquid Molybdenum-based Precursor containing Molybdenum as metal.

[0074] DESCRIPTION OF THE FIGURES

[0075] Figure 1 shows a conventional configuration of hydroconversion process according to the PRIOR ART of the

[0076] EST process;

[0077] Figure 2 shows one embodiment of the method of the invention and the relevant configuration of plant wherein OFF with no solvent is applied to the conventional purge stream from distillate residue of EST process;

[0078] Figure 3 shows another embodiment of the method of the invention and the relevant configuration of the plant wherein CFF with no solvent is applied to the bottom stream from Low pressure Slurry Purge Separator (LPSPS) fed by the lateral bleed (purge) of a reactor of the EST process;

[0079] Figure 4 shows another embodiment of the method of the invention and the relevant configuration of the plant wherein CFF with no solvent is applied to the slurry bottom of a conventional HLPS separator of the EST process;

[0080] Figure 5 shows another embodiment of the method of the invention and the relevant configuration of the plant wherein CFF with no solvent is applied to a portion of the slurry bottom of HLPS column and / or to a portion of slurry stripping column of the EST process;

[0081] Figure 5A shows another embodiment of the method of the invention and the relevant configuration of the plant wherein diaf iltrat ion is applied to the conventional purge stream of EST process;

[0082] Figure 5B shows another embodiment of the method of the invention and the relevant configuration of the plant wherein

[0083] CFF followed by diaf iltrat ion is applied to the conventional purge stream of EST process.

[0084] In the method of hydroconversion according to the present invention, the feeding of Molybdenum-based Precursor of catalyst and the feeding of the heavy charge can be carried out directly to said slurry reactor, contemporaneously or subsequently one to another, without departing from scope of the present invention.

[0085] Alternatively, the feed of said catalyst precursor and the feed of said heavy charge may be first mixed together in a mixing device or in a mixing vessel 20 which may also be fed with a recycle stream 11, and then the mixture of the feeds (i.e. combined feed) is sent to the hydroconversion reactor .

[0086] In one preferred embodiment of the present invention, the hydroconversion reactor is fed with the combined feed contained in the mixing vessel 20, said combined feed comprising the catalyst precursor, the heavy charge (or fresh heavy charge of make-up) and a recycle stream.

[0087] The hydroconversion of heavy charges containing asphaltenes (i.e. heavy oil products) according to the present invention is carried out in compliance with the EST process and it is preferably carried out in a bubble column reactor, including the solid accumulation reactor. One or more hydroconversion slurry reactors placed in parallel can also be used, without departing from the scope of the invention.

[0088] The feedstock to be converted is preferably continuously fed to the reactor (s) .

[0089] In the reactor (s) , the feedstock is put in contact with hydrogen or a stream comprising hydrogen, in the presence of the catalyst under suitable temperature and pressure conditions .

[0090] The hydroconversion reactor can operate within a temperature range comprised between 420°C to 440°C, and a pressure range comprised between 155 atm and 160 atm.

[0091] In the hydroconversion reaction of the method according to the present invention, the Molybdenum-based Precursor of catalyst is generally a liquid oleo-soluble which may react in situ with the sulphide contained in the heavy oil feedstock and with the hydrogen present in the reactor to form M0S2 (solid molybdenite finely dispersed in the liquid phase) in lamellas.

[0092] The normally used precursor is a solution of Mo-octoate (2-ethylhexanoate) in 2-ethylhexanoic acid, containing 15.5% by weight of Molybdenum, even if this is not a limitation of the scope of the invention.

[0093] Thus, the dispersed hydrotreating unsupported catalyst in form of slurry may be generated "in situ" by the oil soluble Mo-containing precursor which has been supplied to the hydroconversion reactor directly or indirectly with the combined feed.

[0094] The particles of the unsupported catalyst have average dimensions within about 5-40 micron.

[0095] In one embodiment of the present invention, and with refence to figure 1, the separation of distillates from slurry phase of the effluent of hydroconversion reaction includes the step of sending the effluent 1 from the reactor to a first phase separator operating at high temperature and high pressure, namely a Hot high pressure separator (HHPS) , in order to separate a vapour phase 2' from a heavy fraction in form of a slurry phase 2: the separated vapour phase 2' is sent from said first phase separator HHPS to a gas treatment section to separate a liquid fraction from the hydrogen-containing gas.

[0096] The first phase separator HHPS can operate within a temperature range comprised between 420°C to 440°C, and a pressure range comprised between 155 atm and 160 atm.

[0097] The slurry phase 2 exiting the first phase separator HHPS is sent to a second phase separator operating at lower pressure which is the Hot low pressure separator (HLPS) to separate a vapour phase from the slurry phase 7.

[0098] In one embodiment of the method of the present invention, the second phase separator HLPS may also be fed with the slurry phase from a Low pressure Slurry Purge Separator

[0099] (LPSPS) , if present.

[0100] Said additional separator LPSPS has generally the function of holding up the lateral bleed stream 5 (i.e. partial flushing) , if any, which may be generally provided on the reactor in order to avoid the accumulation of solids in the bottom of reactor since the slurry catalyst used in the EST process is not confined in the bubble column reactor but follows the flow of the heavy liquid stream as dispersed solids, in particular when the feedstock includes solids of different nature and dimensions, e.g. plastics particulate.

[0101] It is known that increasing the hydrocracking temperature to increase the productivity causes, in particular above certain limits, a marked formation of coke and also insoluble asphaltene resins which can greatly limit the possibilities of use of high catalytic concentrations.

[0102] For example, in order to maintain a level of metal sulfides compatible with the operability of the reaction cycle, at least one partial bleed is provided in the reactor and effected on said stream containing the solids, from which an aliquot of catalyst is inevitably subtracted and thus it must be integrated.

[0103] The slurry phase 7 exiting from HLPS is sent to a slurry stripper to separate light compounds from the heavy phase 8 which is in the form of slurry phase. The slurry phase 8 which leaves the bottom of the slurry stripper is sent to a distillation tower to be fractioned with the aim of separating the VGO, LVGO from the heavier products: the vacuum gas oil (VGO) and the LVGO is thus separated from the bottom distillation residue 9 which is a slurry phase containing the dispersed catalyst as well as unconverted feed and solids in general.

[0104] The first separator at high temperature and high pressure (HHPS) operates at a temperature ranging from 400°C to 450°C, e.g. 425°C, and at a pressure ranging from 12 to 20 MPa (g) , e.g. 15, 8 MPa (g) .

[0105] The second separator Hot low pressure separator (HLPS) operates at a temperature ranging from 370°C to 400°C, e.g. 380°C, and at a pressure ranging from 1 to 0, 5 MPa (g) , e.g. 0,4 MPag.

[0106] The slurry stripper is the third phase separator and operates at a temperature ranging from 320 to 370°C, e.g. 345°C, and at a pressure ranging from 0, 1 to 0, 5 MPa (g) , e.g. 0,25 MPa (g) .

[0107] The stripping in the slurry stripper is carried out by means of steam, as stripping agent, which generally enters the bottom of the slurry stripper in counter current with the fluid containing the compounds to be stripped.

[0108] The operating conditions in the slurry stripper of the

[0109] EST process are generally as follows - Temperature in the range of 380°C;

[0110] - Pressure in the range of 3 bar (g) .

[0111] The distillation tower generally operates at a pressure ranging from 0.0001 to 0.5 MPa (absolute) , preferably from 0.001 to 0.3 MPa (absolute) .

[0112] In one embodiment, the distillation tower is a vacuum distillation tower operating under vacuum conditions.

[0113] As stated above, said primary solid-liquid separation applied to a slurry stream or a purge as provided in the method according to the present invention allows to obtain an outlet solid-rich stream which is more concentrated in term of solids and, on the other side, an outlet cleaned permeate fluid containing no solids or negligible amounts of solids .

[0114] Said primary solid-liquid separation can be selected from

[0115] - cross flow filtration (CFF) without solvent, or

[0116] - diaf iltrat ion with a solvent, or

[0117] - cross flow filtration (CFF) without solvent followed by a subsequent diaf iltrat ion with a solvent.

[0118] The cross-flow filtration of a slurry hydroconversion reaction system provides an outlet slurry stream which is more concentrated in term of solids and, on the other side, an outlet cleaned permeate fluid containing no solids or negligible amounts of solids. In cross-flow filtration the slurry stream flows parallel to the filter medium. The filtrated products (cleaned permeate or filtrated stream) leave the filtration module at right angle to the filter, in this way cross flow filtration prevent a filter-cake build-up.

[0119] The cross flow filtration of the slurry stream in the method according to the present invention is conducted in the absence of any added solvent and may be conducted in one or more CFF devices such as a cross flow filter having one or more substantially tubular membrane filter (s) or membrane filter (s) with a pleated membrane structure, or membrane filter in a spiral wound form, having an outer housing, an inlet (feed) , a retentate outlet and a permeate outlet (filtrate) as disclosed, for example, in US2009159505A1 (Chevron) herein incorporated by reference. The operating temperature of the cross flow filtration is the temperature of the slurry stream entering the CFF device (s) as well as the pressure.

[0120] The design of the filter membrane of the CFF device is such that only the liquid could permeate through the walls of the tube into the shell side of the bundle while the solids are retained on the tube side.

[0121] Thus suitable operating pressures for the CFF applied to a slurry stream or pitch stream (purge stream) exiting from the EST process ranges from 100 to 400 psig (from about 7 barg to about 28 barg) .

[0122] Preferred examples of filter membrane of CFF device (s) usable in the present invention are those made of stainless steel 316, even though materials other than metals can be employed such as polymers, organic materials, inorganic ceramic materials.

[0123] In one embodiment the solid-liquid separation unit, e.g. CFF device, used in the present invention concentrates the solid content from the initial concentration of 5-12 wt . % of the inlet stream, i.e. purge or slurry stream, up to 20-25% by weight of the outlet stream (retentate) while obtaining an outlet cleaned stream containing no solids: thus the content of solids (kg / h) entering the solid-liquid separation unit via the purge stream or slurry stream is assumed to exit from said solid-liquid separation unit only via the retentate, e.g. HSC purge.

[0124] The amounts of solids contained in the retentate are mainly determined by the pore size of one or more filter membrane comprised in the solid-liquid separation unit: said size is selected in such a way to remove at least 50%, preferably 65%, more preferably 75-80%, of the heavy oil from the purge stream and / or slurry streams.

[0125] The diaf iltrat ion with solvent may be conducted in one or more diaf iltrat ion unit (s) : the operating temperature is the temperature of the slurry stream entering the diaf iltrat ion device as well as the pressure.

[0126] Preferred examples of filter membrane of diaf iltrat ion device (s) usable in the present invention are those made of stainless steel 316, even though materials other than metals can be employed such as Polymers, organic materials, inorganic ceramic materials.

[0127] In the diaf iltrat ion unit, a solvent is requested and used as extracting medium for the extract ion / separat ion of the heavy oil from the solids.

[0128] The solvent / extraction medium (solvent 40 in fig. 5A) is a composition comprising a light specific gravity solvent or solvent mixtures, such as, for example, Xylene, benzene, toluene, kerosene, reformate (light aromatics) , light naphtha, heavy naphtha, light cycle oil (LCO) , medium cycle oil (MCO) , propane, diesel boiling range material, which is used to "wash" the feed stream to the deoiling Zone.

[0129] Diaf iltrat ion comprise a filter membrane that may have the same characteristics of the CFF membrane above described.

[0130] Diaf iltrat ion generally generates two product streams:

[0131] - A first stream which is composed of a mixture of solid- free heavy oil and solvent, wherein the solvent may be further recovered from said mixture in a downstream distillation unit and reused whereas the separated solid-free heavy oil is a solid-free lean liquid / st ream that may be used as indicated above. - A second stream which is composed of solids in solvent (clean slurry) solid-rich st ream wherein the solvent may be further recovered from said solids by using a dryer in order to separate the solvent (reusable) from the solids which may be sent to downstream application. The operating temperature of the dryer depends on the boiling point of the solvent used in the diaf iltrat ion as extracting medium.

[0132] Advantageously, the method of the present invention allows to reduce the purge percentage to a value comprised between 2% and 6% with respect to the fresh feed, when liquid solid separation is applied to purge: thus it allows to increase the overall conversion - that can be obtained under conventional operating conditions of EST process - to values that vary from 94% to 98%.

[0133] The clarified component (i.e. the solid-free lean liquid / st ream) , being a product deriving from a separation unit placed downstream the hydroconversion reactor, contains low reactive asphaltenes with respect to the fresh feed. Therefore, the recycle of the clarified component to the slurry hydroconversion section increases the amount of low reactive asphaltenes entering the hydroconversion section.

[0134] With reference to figure 1, it will be now described the process of EST technology known in the art.

[0135] The precursors of a catalyst based on Molybdenum (not showed) , heavy oil products (FEED) , a hydrogen-containing stream (not showed) and a recycle of the distillation residue are supplied to a slurry-phase hydroconversion reactor (REACTOR) in which they are converted, producing reaction effluent 1.

[0136] Generally, the produced reaction effluent 1 is subsequently sent to a high pressure and high temperature separator (hot high pressure separator, HHPS) in order to be separated into a vapour phase 2' (head) and a slurry phase 2 (bottom) .

[0137] The separated vapour phase from HHPS is subsequently supplied to a gas treatment section which has the function of separating a liquid fraction 3 from the hydrogencontaining gas 4.

[0138] A reactor lateral bleed 5 may be provided on the reactor in order to mitigate an abnormal solid accumulation in the Slurry Bubble Column Reactor. Thus, in the EST process the Slurry Bubble Column Reactor is generally equipped with said lateral bleed line 5 which is normally a No Flow line (empty line) during normal operation.

[0139] Said lateral bleed stream 5 is sent to a Low pressure slurry purge separator (LPSPS) in order to separate a vapour phase (not shown) and a slurry phase 6 (bottom) .

[0140] The bottom slurry phase 6 from said LPSPS separator is sent to HLPS separator to separate a vapour phase comprising mainly Atmospheric Gasoil and light ends and a slurry phase

[0141] 7 which is sent to the slurry stripper to separate the lights hydrocarbons, e.g. mainly Atmospheric Gasoil and light ends.

[0142] The high temperature and low pressure separator (HLPS) works as an accumulator: the separated vapour phase exiting the head of said HLPS is supplied into a pre-flash column.

[0143] In the slurry stripper it occurs the separation of a vapour phase comprising mainly Atmospheric Gasoil and light ends (head) and of a slurry phase 8 (bottom) which is an enriched stream: the slurry phase 8 is then sent to the vacuum tower of distillation (VACUUM TOWER) to separate a gas phase comprising VGO, LVGO (head) and a slurry phase 9 (bottom) which is a distillation residue.

[0144] The slurry phase 9 from the bottom of the vacuum distillation tower is then split into a purge stream 10 and a recycle slurry stream 11 which is composed of heavier products .

[0145] The recycle slurry stream 11 is recycled to the combined feed tank 20 to be mixed with the fresh feed of make-up in order to obtain the stream 21 feeding the reactor.

[0146] Generally, the purge stream sent to the battery limits constitutes a percentage that varies from 6% to 8% with respect to the feedstock stream whereas the recycles stream 11 varies from 92% to 94% with respect to the feedstock stream . The series of decreasing pressure and temperature separator devices allows to separate heavier products rich in asphaltenes (vacuum Residue) which also include unconverted feed, metal sulphides, catalyst and solids formed during the hydroconversion reaction (slurry phase 9) from the Vacuum Gas Oil (VGO) fraction and Light Vacuum Gas Oil (LVGO) fraction.

[0147] In the following description of the configurations performing the method according to the present invention, the same reference numbers of figure 1 will be used in the subsequent figures 2 to 5B to identify the same features / elements .

[0148] With reference to figure 2, it is described a first configuration (SCHEME 1) of the present method of hydroconversion and the relevant plant configuration wherein a cross flow filtration without solvent (CEE) is applied to the purge stream 10 which is a portion of the slurry stream 9 exiting the bottom vacuum tower, i.e. the purge stream is a portion of the distillate residue.

[0149] The CEE produces:

[0150] - an outlet stream 12 containing a higher percentage of solids (High Solid Content Purge) than the untreated purge 10 since the same amount of solids entering the CEE unit is designed to exit in the HSC purge stream 12 containing however lower amount of heavy oil with respect the purge 10 entering the CFF; and

[0151] - a cleaned permeate stream 13, i.e. a filtered stream, containing a lower amount of solids or a quite null content of solids with respect to the untreated purge 10.

[0152] The cleaned permeate 13 of said cross filtration is advantageously recycled to the hydroconversion reactor in addition to a portion 11 of the distillation residue 9 that is conventionally recycled back to the reactor, i.e. the remaining portion 11 of the obtained distillate residue 9 that has not formed the purge 10: as shown in the examples, the recycle of cleaned permeate stream 13 allows to improve the conversion of the method of the invention with respect to the conventional EST process.

[0153] The application of cross flow filtration without solvent on a purge stream of a hydroconversion process is particularly advantageous when the purge has a content of solids higher than that in conventional purge of EST process, e.g. 12% of solids vs. conventional 5-6% of solids in the purge of hydroconversion of EST process.

[0154] As alternative, using the same process, CFF and configuration described above for fig. 2, it is possible to valorize the cleaned permeate - as a High Sulphur Fuel oil (HSFO) - if cleaned permeate is sent to the battery limit to leave the process / plant as a product as such rather than being recycled to the reactor as in SCHEME 1.

[0155] If the cleaned permeate is the filtered Vacuum Tower Bottom, some upgrading and blending are needed since the API is low.

[0156] This alternative embodiment of valorizing the cleaned permeate as product is advantageous in case the purge stream 10 constitutes a percentage with respect to the feedstock that is much higher than the conventional percentage, i.e. 30% vs. conventional 6-7%, and the percentage (portion) of the recycle stream 11 to hydroconversion reactor is much lower than conventional, i.e. 70% vs. conventional 92-94%.

[0157] With reference to figure 3, it is described a second configuration (SCHEME 2) of the process and plant of the present invention wherein the CEE without solvent is applied to the bottom stream 6 exiting the bottom of the Low pressure Slurry Purge Separator (LPSPS) which is fed with the EST reactor lateral Bleed stream 5 departing from the bottom part of the slurry bubble column reactor.

[0158] This configuration is particularly advantageous if the heavy charge shows inhomogeneity in terms of composition inside the reactor such as, for example, when some plastic materials are included in the heavy charge: in this case the bottom part of the reactor contains denser phases and particles with the highest particle size with respect to the catalyst particles. The plastic materials in fact remain as a solid if they are unconverted in the reactor and, in addition, they contain many inorganic components such as calcium, sodium, aluminum, titanium, chromium, lead, silicon and other elements as inorganic fillers or as plastic materials contaminants.

[0159] Some of the compounds which contain these elements could have also a particle size which makes suspension difficult, and therefore tends to accumulate on the bottom part of the slurry bubble column reactor.

[0160] The slurry stream 6 exiting the bottom of LPSPS is fed to the CFF unit to produce:

[0161] - a High Solids Concentrated (HSC) Stream 14 that can be partially or totally recycled to the hydroconversion reactor in addition to a portion 11 of distillation residue 9 that does not form the purge 10 ;

[0162] - a cleaned permeate 17 which can be fed to separation section, preferably to the slurry stripper placed upwards the vacuum distillation tower.

[0163] It is preferred that said HSC stream 14 is divided into two streams 15 and 16, one forming the HSC purge 15 and the other forming the recycle (HSC recycled) 16 to the combined feed vessel 20.

[0164] Using a Cross Flow Filtration without solvent on this slurry stream 6 which has substantially the same composition of the reactor lateral bleed stream 5, it is possible to reduce Solid accumulation in the Slurry Bubble Column Reactor as illustrated in the examples.

[0165] With reference to figure 4, it is described another embodiment of the method of the invention and the relevant configuration plant (SCHEME 3) wherein the CEE without solvent is applied to the slurry bottom stream 7 of HLPS in order to obtain a cleaned permeate 19 and a High solid Concentrated (HSC) Stream 18.

[0166] The High Solid Concentrated (HSC) Stream 18 is divided into two streams 18' and 18", one stream (portion) forming the HSC purge 18' and the other stream 18" (remaining portion) forming the recycle (HSC recycled) to the combined feed tank 20 and thus to the hydroconversion reactor.

[0167] The cleaned permeate 19, i.e. solid-free lean liquid / stream, is sent to the downstream fractionation section, in particular to the slurry stripper: then the bottom slurry stream 19" is sent from the slurry stripper to the vacuum tower to obtain, as residue of distillation, a high sulphur Fuel oil (HSFO) containing no solids which can be valorized as a product per se (as such) .

[0168] This high sulphur fuel oil (HSFO) may also be partially recycled upstream to be mixed with the HSC recycle and fresh heavy charge in the combined feed vessel 20 to form the combined feed for the hydroconversion reactor.

[0169] This configuration is particularly advantageous since the Cleaned permeate 19 being a clean fluid, allows to keep the distillation vacuum tower clean.

[0170] With reference to figure 5, it is described another embodiment of the method of the present invention and the relevant plant configuration (SCHEME 4) wherein the CEE without solvent is applied only to

[0171] - a portion 30 of the bottom slurry stream 7 exiting from the bottom of HPLS (dotted line) ; or

[0172] - a portion 31 of the bottom slurry stream 8 exiting from the slurry stripper; or

[0173] - a combined stream 32 of a portion 30 of the bottom slurry stream from HPLS and a portion 31 of the bottom slurry stream from slurry stripper.

[0174] The CEE without solvent produces a Cleaned Permeate 33, i.e. a solid-free lean liquid / stream, and a concentrate 34, i.e. a solid-rich stream.

[0175] The concentrate 34 is the new purge stream (HSC purge) .

[0176] The Cleaned Permeate 33, which is free of solids, can be

[0177] - totally sent as feed to distillation vacuum tower together with a portion of the bottom slurry stream 8 from slurry stripper , or

[0178] - used for fuel oil or for other application; or

[0179] - partially sent to vacuum tower and partially used as fuel oil .

[0180] The configuration of SCHEME 4 is particularly advantageous when the conventional Purge of EST process exiting from the bottom of distillation tower is too viscous, e.g. higher than 10 cSt at CFF operating temperature: in that case it could be problematic to apply the CFF unit to the purge stream 10 as in Scheme 1 of figure 2 since the flux could be not feasible in crossflow filtration.

[0181] In the present invention, it is preferable that at the CFF operating temperature, the viscosity of the slurry fed to the CFF unit is lower than 5 cSt .

[0182] Accordingly, the feed to CFF may be a lighter stream such as the slurry stream from bottom HLPS (Dotted line) and / or from bottom slurry stripper (Solid line) , both having a lower viscosity than that of the purge 10 of the known EST process in figure 1.

[0183] As stated above, in one embodiment of the method of the present invention, in the previous SCHEMES 1 to 4 of fig. 2 to 5 the CFF may be directly replaced by diaf iltrat ion (including a drier) or by the combination of CFF followed by diafiltration.

[0184] In one embodiment of the invention, with reference to the SCHEME of figure 5A, the method of the invention as above described provides that a Diafiltration is applied to EST purge 10 in place of the CFF, generating two products:

[0185] - a mixture 41 of solid-free heavy oil (HO) and light solvent 40. Light solvent 40 may be separated from the solid-free heavy oil in distillation unit downstream the vacuum distillation unit (VDU) and reused.

[0186] After removing light solvent, the solid free heavy oil should be the same as the permeate from concentration stage and can be used in similar applications.

[0187] The obtained solid-free heavy oil is then sent to downstream application;

[0188] - a slurry, i.e. clean slurry 42, of solids in light solvent 40. The solids and light solvent are advantageously separated in a dryer operating at temperature and pressure adapted to evaporate the specific solvent 40 that has been used. The recovered light solvent 40 is reused. The solids are sent to downstream application, e.g. recovery of metals.

[0189] In one embodiment of the invention, with reference to the SCHEME of figure 5B, the method of the invention as above described provides that a Diaf iltrat ion (including a drier not shown in fig. 5B) follows downstream the CEE unit in order to further treat by diaf iltrat ion the HSC purge 12 exiting the CEE (SCHEME 5B of fig.5B) . Diaf iltrat ion applied to the HSC purge 12 exiting the CEE unit generates two products :

[0190] - a mixture 43 of solid-free heavy oil (HO) and light solvent 40, i.e. a solid-free lean liquid / stream . Light solvent 40 may be separated from the solid-free heavy oil in distillation unit downstream the vacuum distillation unit (VDU) and reused. The solid-free heavy oil is then sent to downstream application.

[0191] - a clean slurry 44 containing solids in light solvent, i.e. a solid-rich stream. The solids and light solvent may be separated in a dryer and the light solvent may be reused. The obtained solids are then sent to downstream application, i.e. for recovery of metals.

[0192] The operating temperature of the dryer highly depends on the solvent to use: for toluene, it is dried at low pressure, e.g. atmospheric pressure, and up to 400~500°F ( 2050C-2600C) .

[0193] Some examples of the present invention are now described which have purely descriptive and non-limiting purposes and which represent the preferred embodiments.

[0194] EXAMPLES

[0195] CHARACTERISATION AND MATERIALS

[0196] - The following data have been obtained by simulation using

[0197] ASPEN CUSTOM MODELER® commercialized by Aspentech.

[0198] - The conversion of the process and reported in the following tables may be calculated as follows

[0199] (1-Purge (t / h) / Fresh_Feed (t / h) ) *100 the "Fresh Feed" being that denoted in fig. 1 as FEED, or, alternatively, by using the formula in the respective tables, the result being the same. EXAMPLE 1: Overall Conversion

[0200] It is reported a comparison between the configuration of the known EST process illustrated in fig. 1 and the configuration of one embodiment of the method of the invention illustrated in figure 2 (SCHEME 1) as regards the conversion of process.

[0201] According to the EST process of the prior art in fig.l, the purge stream 10, which is sent to the battery limits, constitutes a percentage that varies from 6% to 8% with respect to the fresh feedstock stream (FEED) , that is allowing a process conversion that varies from 92% to 94%. See for example what is reported in US 2021 / 0395623 Al.

[0202] The configuration in figure 2 according to one embodiment of the method of the present invention differs from the known configuration of figure 1 in that a CEE is further included in the process (and in the relevant plant) and is applied to the purge stream 10 to treat it.

[0203] At the end of CEE operation and at the outlet of the CEE unit in the configuration of fig. 2, it is obtained:

[0204] - a HSC Purge 12, i.e. a purge stream containing a higher amount of solids than the untreated purge 10; and

[0205] - a cleaned permeate 13 which is free of solids, or a quite null content of solids, with respect to the untreated purge 10.

[0206] The comparison of the conversion data is effected in this example by considering the same operating conditions in the reactor, HHPS, LPSPS, HLPS, slurry stripper and vacuum tower, and the same flow rates of fresh feed and by considering to use a CFF device able to concentrate the solid content from the initial concentration (reported in the following table 1) to 20% by weight with respect to the weight of the outlet HSC purge stream: by increasing the solid concentration of four times, the flow rate of the purge stream leaving the CFF is reduced of about four times . This allows to recover much more oil from the slurry than in the conventional EST process with purge.

[0207] In this example, the content of solids (kg / h) entering the CFF via the purge stream 10 is assumed to exit from CFF only via the HSC purge 12 with a concentration of 20% wt . of solids with respect to the HSC Purge.

[0208] The solid content in filtration is not really related to operating conditions. As long as the liquid can be removed, solid content will go up.

[0209] The comparison data are reported here below in table 1.

[0210] Table 1: Increasing Overall Conversion

[0211] EXAMPLE 2 : Obtaining cleaned High Sulphur Fuel oil (HSFO)

[0212] It is reported a comparison as regards the conversion between the configuration according to the prior art of figure 1 and the configuration of figure 2 according to the present invention except for the fact that the cleaned permeate is sent to the battery limits (not illustrated in fig.2) in order to be now alternatively valorized as product like a High Sulphur Fuel oil (HSFO) rather than being recycled to the reactor.

[0213] The comparison of the conversion data is effected in this example by considering the same operating conditions in the reactor, HHPS, LPSPS, HLPS, slurry stripper and vacuum tower, and the same flow rates of fresh feed and recycle (same recycle ratio) and by using a OFF device able to concentrate the solid content from the initial concentration (reported in the following table 2) to 20% by weight with respect to the weight of the outlet HSC purge stream.

[0214] Also in this example, the content of solids (kg / h) entering the CFF via untreated purge 10 is assumed to exit from CFF only via the HSC purge 12 with a concentration of 20% wt . of solids with respect to the HSC Purge: however, in this example it is assumed that in the EST process of prior art the purge stream 10 of fig. 1 which is sent to the battery limits is a percentage (with respect to the fresh feedstock) much higher, i.e. 30%, and accordingly the concentration of solids in said purge stream 10 is much lower than in configuration of example 1. In those conditions the process conversion of the feedstock of EST process according to scheme 1 of figure 1 is 70%.

[0215] The comparison data are reported here below in table 2.

[0216] Table 2: Obtaining cleaned HSFO - EXAMPLE SCHEME-1 - EXAMPLE 3 : Reduced Solid accumulation in the Slurry Bubble Column Reactor

[0217] It reported a comparison of performances between the configuration of known EST process of figure 1 and the configuration of figure 3 (SCHEME 2) of the method according to the present invention.

[0218] Considering

[0219] - a feedstock with the composition reported in Table 3;

[0220] - a slurry bubble column reactor with volume of the bottom of 30 m3;

[0221] - a fresh feedstock flow rate of 7, 5 t / h (not containing solids ) ; and

[0222] - an acceptable volume occupation of the bottom slurry column reactor by solids of 5%, it is reached the maximum acceptable solid occupation in 2 / 3 days if no lateral bleed of reactor is provided in the configuration of the prior art of fig.l.

[0223] Table 3: typical composition of the feedstock including plastic materials Considering 1 t / h of Reactor lateral bleed flow rate with an initial concentration in solids of 5% wt . , and applying the CFF process to said Reactor lateral bleed, in particular to the slurry stream 6, to obtain an outlet slurry 14 from CFF with a concentration of solids of 20% wt . , it results that the flow rate of the outlet High Solids Concentrated Stream (slurry stream 14) is only 0,25 t / h whereas the flow rate of the cleaned permeate 17 is 0, 75 t / h .

[0224] This High Solids Concentrated Stream (HSC stream 14) is advantageously partially recycled (HSC stream 16) to the combined feed tank and partially purged (HSC Purge stream 15) whereas the cleaned permeate 17 is fed to the slurry stripper .

[0225] The configuration of fig. 3 is advantageous in that it allows to reduce Solid accumulation in the Slurry Bubble Column Reactor.

[0226] The comparison data are reported here below in table 4.

[0227] Table 4: Reduced Solid accumulation in the Slurry Bubble Column Reactor - EXAMPLE SCHEME-2 -

[0228] With the Cross Flow filtration applied to the bottom stream 6 of LPSP as in figure 3, it is possible to stabilize the concentration of solids at the bottom of the reactor up to a certain value.

[0229] Moreover, the above configuration is also advantageous since the feed to the slurry stripper (cleaned permeate) contains no solids with respect to the slurry stream 7' from HLPS, which is sent to the stripper as well: thus the concentration of solids of the slurry stream 7' is diluted by the cleaned permeate 17 so that less fouling of the stripper will occur in this configuration.

[0230] EXAMPLE 4 : Reduced solid circulation in the downstream section

[0231] It reported a comparison of performances between the configuration of known EST process of figure 1 and the configuration of figure 4 according to the method of the present invention.

[0232] In the configuration of figure 4 (SCHEME 3) , the CEE is applied to the slurry bottom stream 7 of HLPS in order to obtain a cleaned permeate 19 and a High solid Concentrated (HSC) Stream 18.

[0233] Filtering the slurry bottom stream 7 of HLPS allows to concentrate the solids in the HSC stream 18 while obtaining a cleaned permeate stream 19 to be sent to the slurry stripper.

[0234] Considering 200 t / h of HLPS bottom flow rate having an initial concentration in solids of 7% wt . , and operating with a CFF device to concentrate the solid content to 20% at the outlet of the CFF in an outlet stream 18, it means that thanks to the cross Flow filtration it is possible to avoid the circulation of 14t / h of solids (as indicated in Table 5) in the section downstream the reactor, in particular in the distillation section. Table 5: Reduced solid circulation in the downstream section

[0235] *= recycled back to reactor

[0236] EXAMPLE 5 : Increasing Overall Conversion

[0237] It reported a comparison of performances between the configuration of known EST process of figure 1 and the configuration of the method according to the present invention illustrated in figure 5 (SCHEME 4) .

[0238] The SCHEME 4 of fig. 5 differs from SCHEME 3 of fig. 4, both according to the method of the invention, in the size of CEE required: SCHEME 3 of fig. 4 needs a bigger size since it has to filter all the slurry stream 7 exiting from HPLS, while SCHEME 4 of fig. 5 needs a CEE of smaller size since it processes only a portion 30 of the slurry stream 7 from HPLS and / or a portion 31 of the bottom stream 8 from slurry stripper in order to recycle the Cleaned Permeate 33, thus increasing the overall conversion.

[0239] The comparison data between the SCEME of fig. 1 and the SCHEME 4 of fig. 5 are reported here below in table 6.

[0240] Table 6: Increasing Overall Conversion

[0241] The total amount of solids (kg / h) in the stream entering the CFF is assumed to correspond to the amounts of solids leaving the CFF through the purge stream and it is considered to use a CFF device able to concentrate the solids from 5% of the CFF inlet stream to 20% of the outlet purge stream: by increasing the solid concentration of four times, the flow rate of the purge stream leaving the CFF is reduced of about four times. This allows to recover much more oil from the slurry than in the conventional EST process with purge.

[0242] This configuration is advantageous in case the EST Purge has such a high viscosity as to have a feasible flux in crossflow filtration.

[0243] Using the configuration of SCHEME 4 of fig. 5 it is not necessary to purge a stream of distillation residue from Vacuum tower distillation: in this configuration no solid removal from distillation bottom stream is needed as purge stream, contrary to the conventional EST process.

[0244] EXAMPLE 6 : Increasing Overall Conversion with

[0245] Diaf iltration

[0246] It illustrates the configuration of the method according to the present invention wherein in one of the previous Scheme 1 to 4 the CFF is replaced by diaf iltration (including a drier) .

[0247] In particular, the present example refers specifically to SCHEME 5A of figure 5A: fig. 5A substantially represents the same configuration of SCHEME 1 of fig. 2 wherein CFF is replaced by diaf iltration .

[0248] In the diaf iltration Zone, an extracting medium (solvent 40) is employed for the extract ion / separat ion of the heavy oil from solids including the spent catalyst.

[0249] Diaf iltration generates two product streams (fig. 5A) : - A mixture 41 of solid-free heavy oil from EST pitch and light solvent.

[0250] Light solvent (i.e. the solvent 40) is recovered in a downstream distillation unit (not shown in the fig. 5A) and reused. The solid-free heavy oil which is recovered from EST purge may be sent to downstream applications (not shown in fig. 5A) .

[0251] - A slurry solids 42 in light solvent (clean slurry) . The solids and light solvent are separated in dryer.

[0252] The solids are rejected in solid state from the drier.

[0253] The light solvent is reused. The solids are sent to downstream applications (not shown in fig. 5A) . The comparison data are reported here below in table 7.

[0254] Table 7 : Replacement of the CFF in Scheme 1 with

[0255] Diafiltration and Drier - EXAMPLE SCHEME 5A

[0256] EXAMPLE 7 : Increasing Overall Conversion

[0257] It illustrates the configuration of the method according to the present invention wherein in one of the previous Scheme 1 to 4 the CFF is followed by diafiltration (including a drier) . In particular, the present example refers specifically to SCHEME 5B of figure 5B: fig. 5B substantially represents the same configuration of SCHEME 1 of fig. 2 wherein the diaf iltrat ion (including a drier not shown) is provided directly downstream the CEE in the SCHEME 1 of fig. 2 in order to treat by diaf iltrat ion the HSC purge stream 12 exiting the CEE unit.

[0258] In the diaf iltrat ion Zone, an extracting medium (solvent 40) is employed for the extract ion / separat ion of the heavy oil from solids including the spent catalyst.

[0259] Diaf iltrat ion generates two product streams (fig. 5B) : - A mixture 43 of solid-free heavy oil (HO) from HSC Purge and light solvent.

[0260] Light solvent (i.e. the solvent 40) is recovered in a downstream distillation unit (not shown in the fig. 5B) and reused. The solid-free heavy oil (HO) which is recovered from HSC purge may be sent to downstream applications as high sulphur fuel oil (HSFO, not shown in fig. 5B) or can be recycled to the reactor.

[0261] - A slurry solids 44 in light solvent (clean slurry) .

[0262] The solids and light solvent are separated in dryer. The solids are rejected in solid state from the drier. The light solvent is reused. The solids are sent to downstream applications (not shown in fig. 5B) .

[0263] The comparison data are reported here below in table 8. The method of the invention illustrated in the configuration of SCHEME 5B allows to increase Overall Conversion as shown in table 8. Table 8: Added Diaf iltrat ion and Drier after Concentration after CEE in Scheme - EXAMPLE SCHEME 5B -

[0264] The calculation of the conversion for SCHEME 5B, using the above formula

[0265] (1-Purge (t / h) / Fresh_Feed (t / h) ) *100 must be carried out by considering the "Purge" of the above formula as corresponding to the solid stream exiting the dryer of DIAFILTRATION .

Claims

CLAIMS1. Method of hydro-conversion of Heavy charges as feedstock comprising the following steps:(A) Feeding a Molybdenum-based Precursor of an unsupported hydrogenation catalyst containing Molybdenum to a slurry reactor;(B) Feeding a heavy charge comprising asphaltenes to said slurry reactor;(C) Hydrotreating the heavy charge in said slurry reactor in the presence of hydrogen and a dispersed hydrotreating unsupported catalyst deriving from said Molybdenum-based Precursor of catalyst to obtain an effluent (1) of hydroconversion reaction;(D) Submitting the effluent (1) to gas-liquid separation to separate distillates (fractions) in form of Vacuum Gas Oil (VGO) , Heavy Vacuum Gas Oil (HVGO) , Light Vacuum Gas Oil (LVGO) , Atmospheric Gas Oil (AGO) from at least one slurry phase comprising asphaltenes, unconverted feedstock, catalyst and solids formed during the hydroconversion reaction; said gas-liquid separation being carried out in a separation unit comprising a Hot high pressure separator (HHPS) , a Hot low pressure separator (HPLS) , a slurry stripper and distillation vacuum tower in liquid communication with each othersaid gas-liquid separation unit optionally including aLow pressure Slurry Purge Separator (LPSPS) in slurry communication with the reactor, characterized in that said method of hydroconversion further comprises a primary solid-liquid separation to treat- a purge (10) , said purge being a part of a bottom stream (9) of said distillation vacuum tower; or- said at least one slurry phase separated from one or more distillates, said primary solid-liquid separation being selected from- cross flow filtration (CFF) without solvent,- diaf iltrat ion with a solvent, or- cross flow filtration (CFF) without solvent followed by a subsequent diaf iltrat ion with a solvent, said at least one slurry phase previously separated from one or more distillates or a portion (30; 31) of said at least one slurry phase being then submitted to said primary solidliquid separation to separate a solid-rich stream (12; 14; 18; 34; 42; 44) , optionally including said solvent, from a solid-free lean stream (13; 17; 19; 33; 41; 43) , optionally including said solvent; said at least one slurry phase submitted to said primary solid-liquid separation being selected from- the bottom stream (6) from a Low pressure Slurry PurgeSeparator (LPSPS) , if present;- the bottom stream (7) from a Hot low pressure separator (HPLS) ;- a portion (30; 31) of a bottom stream (7; 8) from Hot low pressure separator (HPLS) or slurry stripper;- the combined stream (32) of portions (30; 31) of bottom streams from Hot low pressure separator (HPLS) and slurry stripper.

2. Method according to claim 1, wherein said primary solid-liquid separation is carried out by means of a cross flow filtration (CFF) without solvent and it is applied to said purge stream (10) purged from distillate residue of EST process to obtain a cleaned permeate stream (13) and a High Solid Content Purge (12) , said cleaned permeate stream (13) being recycled to the hydroconversion reactor in addition to a portion (11) of distillation residue (9) or sent to the battery limit as product as such (High Sulphur Fuel oil) .

3. Method according to claim 1, wherein said primary solid-liquid separation is carried out by means of a cross flow filtration (CFF) without solvent and it is applied to a bottom stream (6) from Low pressure Slurry Purge Separator (LPSPS) fed by a lateral bleed stream (5) of a reactor of the EST process to obtain a High Solids Concentrated Stream (14) to be recycled to the hydroconversion reactor and acleaned permeate (17) to feed a slurry stripper placed upwards the vacuum distillation tower.

4. Method according to claim 1, wherein said primary solid-liquid separation is carried out by means of a cross flow filtration (CFF) without solvent and it is applied to a slurry bottom (7) of a HLPS separator of the EST process to obtain a cleaned permeate (19) to feed a slurry stripping column and a High solid Concentrated Stream (18) , one portion (18") of said High solid Concentrated Stream (18) being recycled to the hydroconversion reactor.

5. Method according to claim 1, wherein said primary solid-liquid separation is carried out by means of a cross flow filtration (CFF) without solvent applied to a portion (30) of a bottom slurry stream (7) from HLPS column and / or to a portion (31) of a bottom slurry stream (8) from slurry stripping column of the EST process to obtain a concentrate (34) in the form of a purge stream (HSC purge) and a Cleaned Permeate (33) to feed a distillation vacuum tower and / or to be used as fuel oil.

6. Method according to claim 1, wherein said primary solid-liquid separation is carried out by means of a crossflow filtration (CFF) without solvent followed by diaf iltrat ion and it is applied to the purge stream from distillate residue of EST process.

7. Method according to any one of the preceding claims,wherein the solid content of said purge or said slurry stream entering the solid-liquid separation units is 5-12 wt . % of the inlet stream.

8. Method according to any one of the preceding claims, wherein said solid-liquid separation is carried out via CFF to remove at least 50%, preferably 65%, more preferably 75- 80%, of the heavy oil from a purge stream and / or slurry streams .

9. Method according to claim 8, wherein said solid- liquid separation is carried out via CFF to remove at least50%, preferably 65%, more preferably 75-80%, of heavy oil from a bottom slurry stream (7) of HLPS or from a bottom stream (8) of a slurry stripper to obtain a cleaned permeate stream (19; 33) to be sent, respectively, to said slurry stripper or to a vacuum tower to reduce solid circulation in downstream section comprising said slurry stripper and said vacuum tower.

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