Process for the hydrocracking of hydrocarbon feedstocks

Abstract

A hydrocracking process: A. hydrotreating HDT the feedstocks, B. gas/liquid separation of effluent from A with a separation device having a chamber compartmentalized into an upstream degassing compartment and a downstream stripping compartment, the passage of the degassed liquid from the degassing compartment to the stripping compartment being provided by an opening made in the internal wall and/or by overflowing above the said internal wall separating the said compartments, C. hydrodesulfurization of gaseous effluent obtained in B and of an external feedstock, D. a first hydrocracking of liquid effluent resulting from B, E. gas/liquid separation of liquid effluent from D and of the liquid effluent from C, F. a fractionation of liquid effluent from E, G. a second hydrocracking of unconverted liquid fraction from F.

Claims

1. A process for hydrocracking of hydrocarbon feedstocks containing at least 80% by volume of compounds boiling above 340° C., said process comprising at least the following stages: (A) hydrotreating HDT of said feedstocks, in the presence of hydrogen and of at least one hydrotreating catalyst, (B) gas/liquid separation S1 of effluent from stage A with a separation device (S) which comprises a chamber compartmentalized into an upstream degassing compartment and a downstream stripping compartment separated with an internal wall, degassing liquid effluent from (A), passing degassed liquid from the degassing compartment to the stripping compartment through at least one opening made in the internal wall and/or by overflowing above said internal wall separating said compartments, stripping degassed effluent so as to obtain a gaseous effluent comprising hydrogen and a middle distillate MD fraction and a liquid effluent, and scrubbing by injection of a scrubbing medium in order to condense heavy compounds resulting from the degassing and/or stripping, in a scrubbing compartment, (C) hydrodesulfurizing HDS of the gaseous effluent obtained in stage B and of an external liquid hydrocarbon middle distillate MD feedstock, (D) a first hydrocracking HCK1 of the liquid effluent resulting from stage B in the presence of hydrogen and of a hydrocracking catalyst, (E) a second gas/liquid separation S2 of liquid effluent obtained in stage D and of liquid effluent obtained in stage C in order to produce a liquid effluent and a gaseous effluent comprising at least hydrogen, (F) fractionating the liquid effluent resulting from stage E into at least one effluent comprising converted hydrocarbon products having boiling points of less than 340° C. and an uncoverted liquid fraction having a boiling point of greater than 340° C., (G) a second hydrocracking HCK2 of the unconverted liquid fraction resulting from stage F in the presence of hydrogen and of a hydrocracking catalyst, wherein at least a part of the effluent obtained in the hydrocracking HCK2 is sent to and separated in the separation S2 in (E), (H) compressing the gaseous effluent comprising at least hydrogen obtained in separation S2 and recycling in at least one of the hydrodesulfurization HDS (C), or first hydrocracking HCK1 (D).

2. The hydrocracking process according to claim 1, comprising in stage B separating in a first gas/liquid separation S1 effluent obtained in stage A with the separation device (S), which comprises: a single chamber delimited by external walls and comprising an external inlet for the effluent, an external liquid outlet (7) and an external gas outlet (5), the chamber being oriented along a substantially vertical or oblique axis and being compartmentalized into at least two compartments (a,b) using at least one wall internal to the chamber (P1,P2,P3,P5) and oriented substantially along said axis, the compartments comprising an upstream degassing compartment (a) and a downstream stripping compartment (b), the degassing compartment (a) being in fluidic connection with the external inlet (1) and with a first gas outlet (3) and a degassed liquid outlet (2), the stripping compartment (b) being in fluidic connection with an inlet for degassed liquid (2), a stripping medium inlet (8), a second gas outlet (9) and a liquid outlet (7), the first and second gas outlets (3,9) being in fluidic connection with the external gas outlet (5) of the chamber, the liquid outlet of the stripping compartment (7) being in fluidic connection with the external liquid outlet of the chamber, the passage of the degassed liquid (2) from the outlet of the degassing compartment (a) to the inlet of the stripping compartment (b) being provided by at least one opening (x) made in the wall internal to the chamber (P1,P2,P3) and/or by overflowing above the internal wall (P1) separating the said compartments, so as to obtain a gaseous effluent comprising hydrogen and a middle distillate MD fraction and a liquid effluent.

3. The process according to claim 1, further comprising recycling gaseous effluent comprising at least hydrogen obtained in the separation S2 to hydrotreating HDT (A).

4. The process according to claim 1, in which the hydrocarbon feedstocks treated in the process and sent to the hydrotreating stage A are hydrocarbon feedstocks containing at least 80% by volume of compounds boiling between 370 and 580° C.

5. The process according to claim 1, in which the hydrocarbon feedstocks treated in the process and sent to the hydrotreating stage A are vacuum distillates VDs that are gas oils resulting from direct distillation of crude or from conversion units, distillates originating from desulfurization or hydroconversion of atmospheric residues and/or of vacuum residues, deasphalted oils, feedstocks resulting from biomass or any mixture of at least one of said feedstocks.

6. The process according to claim 1, wherein stage D of the first hydrocracking HCK1 and/or the second hydrocracking HCK2 stage G are carried out at a temperature 320 to 450° C., under a pressure of 3 to 20 MPa, at a space velocity of 0.2 to 4 h.sup.−1 and with an amount of hydrogen introduced at a liter of hydrogen/liter of hydrocarbon ratio by volume of 200 to 2000 l/l.

7. The process according to claim 1, wherein the hydrotreating HDT stage A is carried out as a temperature of 200 to 390° C., under a pressure of 2 to 16 MPa, at a space velocity of 0.2 to 5 h.sup.−1 and with an amount of hydrogen introduced at a liter of hydrogen/liter of hydrocarbon ratio by volume of 100 to 2000 l/l.

8. The process according to claim 1, in which the unconverted liquid fraction resulting from stage F used in the hydrocracking HCK2 stage G comprises at least 95% by weight of compounds boiling at a boiling point of 150 to 380° C.

9. The process according to claim 1, in which the external liquid hydrocarbon feedstock treated in the hydrodesulfurization HDS stage C is a straight run gas oil resulting from direct distillation of a crude oil, light vacuum gas oil or light vacuum distillate, or liquid hydrocarbon feedstocks resulting from a coking unit, from a visbreaking unit, from a steam cracking unit and/or from a catalytic cracking (Fluid Catalytic Cracking) unit, or a gas oil feestock resulting from conversion of biomass.

10. The process according to claim 2, in which the chamber of the said separation device (S) comprises a third scrubbing compartment (c), downstream of the first two compartments (a,b), and positioned above them in the chamber, and optionally comprising a coalescer pad.

11. The process according to claim 10, in which the separation S1 stage B is carried out with the following successive substages: degassing fluid to be separated into a liquid phase and into a gas phase by getting the fluid closer to its thermodynamic equilibrium in the first degassing compartment (a), stripping by injection of a stripping medium in order to evaporate a part at least of light components dissolved in liquid obtained by the degassing stage in the stripping compartment (b), scrubbing by injection of a scrubbing medium in order to condense heavy compounds resulting from the degassing and/or stripping in the scrubbing compartment (c).

12. The process according to claim 1, in which the separation S1 stage B is carried out in the separation device operating at a temperature of 50 to 450° C., and at a pressure corresponding to the outlet pressure of the effluent obtained in the hydrotreating stage A decreased by pressure drops.

13. The process according to claim 10, in which the separation S1 stage B is carried out so that the section for passage of the fluid in the degassing compartment (a) and/or in the stripping compartment (b), and/or in the scrubbing compartment (c), is sufficient to limit velocity of the gas below critical velocity for entrainment of droplets.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail below using nonlimiting examples, illustrated by the following figures:

(2) FIG. 1: a functional representation of the operating principle of the separation device according to a first example according to the invention,

(3) FIGS. 2a, 2b: a first alternative form of the separation device according to the invention, respectively along a vertical section and a horizontal section at mid-height, according to the first example according to the invention,

(4) FIGS. 3a, 3b: a second alternative form of the separation device according to the invention, respectively along a vertical section and a horizontal section at mid-height, according to the first example according to the invention,

(5) FIGS. 4a, 4b: a third alternative form of the separation device according to the invention, respectively along a vertical section and a horizontal section at mid-height, according to the first example according to the invention,

(6) FIG. 5: a fourth alternative form of the separation device according to the invention along a vertical section, according to the first example according to the invention,

(7) FIG. 6: the first alternative form of FIGS. 2a, 2b according to a bird's-eye view with the representation of the liquid streams in the device; according to the first example according to the invention,

(8) FIG. 7: a functional representation of the operating principle of the separation device according to a second example according to the invention,

(9) FIG. 8: a functional representation of a hydrocracking process integrating the separation device of the preceding figures.

(10) The figures are schematic and the different elements represented are not necessarily to scale. The separation device according to the invention, also denoted under the term of separator, defines a chamber, the greatest dimension of which is positioned along a vertical axis X in its operating position, and it is thus that it is represented in the figures. The identical components exhibiting the same meaning retain the same reference from one figure to the other.

(11) In a first step, FIGS. 1 to 7, centred on the separation device used in stage E of the two-stage hydrocracking process of the invention, are described.

(12) FIG. 1 is thus a functional representation of the gas/liquid separation carried out by the separator according to the invention. Let us take the example of a fluid in the form of a two-phase liquid/vapour stream, the ratio of the gas to liquid flow rates by weight G/L of which is between 0.1 and 2 and preferably between 0.5 and 2. The temperature of the stream to be separated is between 20° C. and 600° C., preferably between 150 and 450° C. The pressure of the stream to be separated is between 0.1 and 25 MPa and preferably between 15 and 20 MPa. The stream to be separated is, for example, the effluent from a fixed-bed hydrotreating reactor or the effluent from a fixed-bed hydrocracking reactor.

(13) The separation according to the invention is carried out in three sections (also known as compartments in the description which follows of the different alternative separator forms): a degassing section a, a stripping section b and an optional scrubbing section c. These two or three sections are, according to the invention, integrated in one and the same separator, thus in a single chamber.

(14) The entire separator operates at the same pressure or substantially at the same pressure as that of the incoming two-phase stream 1 to be separated.

(15) The stream to be separated 1 is injected into the degassing section a. The aim of this operation is to carry out a first separation, by allowing the fluid to reach or to approach its thermodynamic equilibrium, in temperature and in pressure. It is then possible to withdraw, from section a, a predominantly liquid stream 2, referred to as degassed liquid, and a predominantly gaseous stream 3.

(16) In order to ensure that this first separation is carried out efficiently, the degassing section a is dimensioned so as to limit the entrainment of liquid droplets in the stream 3: the surface area for passage of the gas stream 3 in section a is chosen to be sufficient to limit the velocity of the gas below the critical velocity for entrainment of the droplets, preferably below 90% of this velocity, more preferably still below 80% of this critical velocity. The critical velocity is defined as the velocity of fall of droplets with a diameter of 100 micrometres in the gas stream at the operating conditions of section a.

(17) It varies as a function of the properties of the gas and of the liquid of the stream to be treated, and also of the operating conditions (flow rate, temperature, pressure, and the like). The passage time of the stream 1 in section a is generally between 30 seconds and 10 minutes; this is a time sufficient for the stream to stabilize thermodynamically and for the degassing to take place, with an upper part containing predominantly gas with a small amount of liquid and, in the lower part, predominantly a liquid, still containing a certain portion of gas, and an interface between these two parts.

(18) In section a, there is thus a lower zone in which, in operation, a continuous liquid phase is found and an upper zone in which a continuous gas phase is found. These two phases are delimited with respect to one another by an interface, which will define the level of liquid in this section. The predominantly liquid stream 2 exiting from section a is subsequently injected into the stripping section b. The objective of this operation is to evaporate a part of the light/gaseous components in the degassed liquid 2. In order to carry out the stripping, a stream 8 of a stripping medium will be injected into section b, this medium being in this instance hydrogen: the injection of hydrogen makes it possible to lower the partial pressure of the gases (hydrocarbons) to be separated and to evaporate them. Section b can optionally be provided with chevrons or trays (such as shower decks, discs and doughnuts, bubble cap trays, valve trays or any other distillation tray technology known to a person skilled in the art).

(19) Other gases than hydrogen can alternatively be chosen as stripping medium, such as, for example, a light gas, such as steam or nitrogen.

(20) The surface area for passage of the gas in section b is sufficient to limit the velocity of the gas below the critical velocity for entrainment of the droplets, preferably below 90% of this velocity, more preferably still below 80% of this critical velocity. The passage time of the liquid in section b is between 30 seconds and 10 minutes.

(21) In section b, in operation, there will also be a lower zone in which a continuous liquid phase is found and an upper zone in which a continuous gas phase is found, the two upper and lower zones being delimited with respect to one another by an interface defining the level of liquid in the stripping section b.

(22) The gas stream 3 resulting from section a is injected, with the gas stream 9 resulting from section b, into the scrubbing section c. This scrubbing stage is optional. It makes it possible to reduce the amount of heavy compounds entrained in the gas stream 5 which exits from the separator. The objective of this stage is to condense the heavy compounds resulting from section a and, to a lesser extent, from section b. This stage also makes it possible to recover the droplets of liquids entrained from these sections. A stream 4 of a scrubbing medium is injected into section c in order to absorb these heavy compounds. This scrubbing medium can be composed of hydrocarbons. Preferably, this stream is a light or heavy vacuum gas oil (LVGO or HVGO), a deasphalted oil (DAO) or a middle distillates cut (gas oil or kerosene), a naphtha or an aromatic oil resulting from a catalytic cracking (LCO/HCO). The scrubbing stream can result from the process where the separator is installed or be imported, for example resulting from a vacuum distillation installed in the hydrocracking process concerned. It can also be an external feedstock which is subsequently treated in reactors installed downstream of the separator, on its gas outlet or on its liquid outlet.

(23) In this scrubbing section c, there is a countercurrentwise contact between a downward liquid phase and an essentially gaseous upward phase, according to a technology known to a person skilled in the art.

(24) Section c is preferably provided with a structured or random packing, preferably a structured packing, maximizing the liquid/vapour exchanges. Section c can also be composed of chevrons or trays (such as shower decks, discs and doughnuts, valve trays or any other distillation tray technology known to a person skilled in the art).

(25) It should be noted that, while section b and section c can both be provided with packings, also known as internal packings, such as those mentioned above, they remain distinct from one another, the inlet/outlet streams which pass through them being different: the stream which passes through section c is predominately, in particular essentially, gaseous, which contains liquid dispersed within it, whereas section b is traversed by a predominantly, in particular essentially, liquid stream with gas dispersed within it.

(26) The surface area for passage of the gas resulting from section c is sufficient to limit the velocity of the gas below the critical velocity for entrainment of the droplets, preferably below 90% of this velocity, more preferably still below 80% of this critical velocity.

(27) Optionally, a coalescer pad (or mesh pad) is installed in the upper part of section c, so as to coalesce the entrained droplets, in order to increase the diameter of these droplets and to limit the entrainment thereof in the gas.

(28) The flow over the packings is of trickling type (the continuous phase is in this instance the gas phase).

(29) In the case where the scrubbing medium is liquid under the operating conditions, the scrubbing oil absorbs a part of the hydrocarbons resulting from sections a and c and makes it possible to prevent the export of droplets in the gas stream 5 exiting from the separator. This makes it possible to increase the velocity of the gases in section a and thus to limit the surface area thereof for passage. Limiting the export of droplets in the gas stream 5 is advantageous for the items of equipment positioned downstream of the separator as this limits the fluctuations in composition and optionally the fouling of these items of equipment.

(30) In the case where the scrubbing medium is partially or completely evaporated in section c, its evaporation makes it possible to accentuate the phenomenon of condensation of the heaviest vapours resulting from sections a and b. In this case, the medium can advantageously be treated in a reactor installed downstream of the gas outlet 5 of the separator (for example a reactor for the hydrodesulfurization of middle distillates).

(31) The temperature of the scrubbing medium stream 4 is preferably less than the temperature of the stream 1 entering the degassing section a, in order to maximize the phenomenon of condensation of the heavy vapours and to thus limit the flow rate thereof. The temperature of the stream 4 can be controlled by a heat exchanger upstream of the injection into the separator.

(32) The temperature of the stream 1 is advantageously between 20 and 600° C. and preferably between 150 and 450° C. The temperature of the stream 4 is advantageously also between 20 and 600° C., thus the same range as for the stream 1. However, preferably, the temperature of the stream 4 is chosen 50° C. colder than the temperature of the stream 1 and more preferably still 100° C. colder than the temperature of the stream 1.

(33) The flow rate of the stream 4 is chosen to be sufficient to obtain a wetting of the packing or of the trays used in section c.

(34) The liquid stream 6 resulting from the scrubbing section c is also injected into the stripping section b. This stream is composed of the compounds condensed in section c and of the non-evaporated scrubbing medium of the stream 4.

(35) A stripping medium can optionally be injected also into the degassing section a.

(36) The temperature of the stripping section b is the thermodynamic equilibrium temperature of the mixture of the streams 2, 6 and 8; it is generally less than the temperature of the degassing section a by a few degrees.

(37) In synthesis, the different stream exchanges/transfers in the three sections of the separator S are thus the following: the fluid to be separated 1 enters, from the outside of the separator, the degassing section a a degassed liquid 2 exits from section a to the stripping section b a gas 3 exits from section a, which gas goes to the scrubbing section c the degassed liquid 2 enters the stripping section b a stripping medium 8 enters the stripping section b a gas 9 exits from the stripping section to the scrubbing section c and a liquid 7 exits from the stripping section to the outside of the separator the gas 3 originating from the degassing section a, the gas 9 originating from the stripping section b and the scrubbing medium 4 enter the scrubbing section a liquid stream 6 exits from the scrubbing section c to the stripping section b and a gas stream 5 exits from the scrubbing section c to the outside of the separator.

(38) Overall, there is thus a two-phase liquid/gas stream 1 entering the separator via the degassing section a, a liquid stream 7 exiting via the stripping section b and a gas stream 5 exiting via the scrubbing section c.

(39) The different alternative separator design forms employing this separation process are described below one by one. In all the alternative forms represented in FIGS. 2 to 6, the separator S exhibits a single chamber with substantially cylindrical side walls, with a bottom wall and an upper wall both slightly rounded/convex, which can thus exhibit a hemispherical or hemi-elliptical shape. This shape means that this type of chamber can also be denoted under the term of knockout “drum”. The separator, in the operating position, is oriented along the X axis of the cylindrical walls, in this instance a vertical axis. Naturally, the invention applies in the same way to separators, the section of which is not cylindrical or which is oriented obliquely with respect to the vertical, and also to separators, the bottom wall and/or the upper wall of which are not rounded but flat, for example.

(40) According to FIGS. 2a and 2b and 6, a first alternative form of separator S is represented with thus its cylindrical side walls L. An internal wall P1 is positioned inside the chamber: it is a flat and vertically oriented wall. In the lower part, it rests on the bottom wall of the chamber, and its upper edge bs corresponds approximately to between half and ⅔ of the height H of the cylindrical side walls L of the chamber. This wall P1 joins, by its two side edges, the side wall of the chamber, and thus defines two coaxial compartments: the degassing compartment a and the stripping compartment b. The compartment a is provided with the inlet 1 for the fluid to be separated.

(41) In the upper part, above the upper edge bs of the internal wall P1, there is found the scrubbing compartment c, as represented in FIG. 6.

(42) The wall P1, as also represented in FIG. 6, is provided with through orifices x distributed over a strip of height h: the position, the size and the distribution of these orifices are chosen so as to allow the degassed liquid 2 to pass from compartment a to compartment b, while keeping the fluid 1 in the degassing compartment for a sufficient residence time. The surface area for liquid passage of the combined orifices x is such that the liquid stream 2 which passes through them is at least equal to the liquid stream coming from the stream 1. Optionally, the orifices x, or at least some of them, are provided with nonreturn valves (not represented) in order to minimize the recirculation of liquid from compartment b to compartment a.

(43) Alternatively, a solid wall P1 is retained and the degassed liquid 2 is transferred from compartment a to compartment b by overflowing of the liquid above the upper edge bs of the internal wall P1, which forms a weir. In this case, the residence time of the fluid in the compartment is a function, in particular, of the height h1 of the upper edge bs in question and, preferably, this upper edge, acting as weir, is equipped with chevrons, so as to stabilize and to homogenize the flow of liquid from compartment a to compartment b.

(44) The upper edge bs of the internal wall P1 is surmounted by a wall d, represented in FIG. 6, which is a wall positioned above the upper edge bs as far as the side walls L of the chamber. It is preferably without contact with the upper edge, for mechanical reasons, but it is also possible to provide a continuity between the upper edge bs and this wall d. This wall d is oriented obliquely towards the centre of the chamber in the form of an inclined tray which separates compartment a from the scrubbing compartment c. This inclined tray is optionally provided with valves and/or with bubble caps in order to allow the gas resulting from compartment a to pass to compartment c but while preventing the passage of liquid from compartment c to compartment a. Preferably, the inclined tray d is not in contact with the internal separation wall P1 between a and b. The angle of inclination of the tray d with respect to the horizontal is between 1° and 45°, preferably between 5° and 30°. In this instance, by way of example, it is approximately 20°.

(45) The surface area for passage of the gas resulting from compartment a to compartment c via the stream 3 is chosen to be sufficient to limit the velocity of the gas below the critical velocity for entrainment of the droplets, preferably below 90% of this velocity, more preferably still below 80% of this critical velocity.

(46) The passage time of the liquid in the stripping compartment b is between 30 seconds and 10 minutes. The stripping medium (stream 8) is injected into compartment b through a diffuser. The liquid draw-off orifice (stream 7) of the stripping compartment b is preferably provided with a conventional anti-vortex device, in order to limit the entrainment of gas in the pipe evacuating the liquid from the compartment. It can be a matter, for example, of cross-braces.

(47) When the scrubbing compartment c exists, as is the case represented in FIGS. 2 and 6, then the scrubbing oil is injected into compartment c via a distribution tray (not represented) which provides a homogeneous distribution over the internal parts of compartment c, which is preferably provided with a structured or random packing, preferably a structured packing, maximizing the liquid/vapour exchanges.

(48) Compartment c can also comprise chevrons or trays, such as shower decks, discs and doughnuts, valve trays or any other conventional distillation tray technology.

(49) The surface area for passage of the gas (stream 5) resulting from compartment c is chosen to be sufficient to limit the velocity of the gas below the critical velocity for entrainment of the droplets, preferably below 90% of this velocity, more preferably still below 80% of this critical velocity.

(50) FIGS. 3a and 3b describe a second alternative form of separator S. Only that which differs from the first alternative form described above will be described. The main difference is the modification in the relative configuration between compartments a and b: in this instance, they are positioned concentrically with the vertical axis of the separator, by an internal wall P2 which defines a cylinder positioned on the bottom wall of the separator and centred on the vertical axis of the latter: there is thus a degassing compartment a on the outside with respect to the vertical axis of the separator, of substantially annular shape and delimited by this wall P2, on the one hand, and by the external side walls L of the separator, on the other hand, and compartment b, which is delimited by the interior space defined by the cylindrical internal wall P2. The inclined wall d2 separating compartment a from compartment c is this time substantially in the form of a frustum, the smaller base of which surmounts the cylindrical upper edge, with or without continuity, of the wall P2 and the greater base of which joins the external side walls L of the separator.

(51) FIGS. 4a and 4b describe a third alternative form of separator S. For this alternative form, only that which differs from the second alternative form described above will be described. In this alternative form, the two compartments a and b are positioned concentrically as in the second alternative form but this time it is compartment b which is of annular shape and which is positioned on the outside and compartment a which is delimited by the cylindrical interior space delimited by the internal wall P3. The inclined wall d3 separating compartment a from the upper scrubbing compartment c this time exhibits the shape of a conical roof which will surmount, at a certain distance, the upper edge bs of the wall P3 while exhibiting, at its base, a diameter slightly greater than that of the wall P3. The gas (stream 3) can thus circulate as represented from compartment a to compartment c while flowing upward between the upper edge of the wall P3 and the base of the roof d3.

(52) FIG. 5 is a fourth alternative form of separator S, where the separation between compartments a and b is carried out using a solid tray P4 positioned substantially horizontally in the chamber and of annular shape and solid form, and provided with a weir consisting of the circular central opening of the solid tray extending upward in a portion of solid cylindrical wall P5 over a given height. The injection of the stream 1 of fluid to be treated is carried out above the tray P4. In the top part of the weir P5, above its upper edge, there is positioned a conical roof d3 of the same design as that used in the preceding alternative form.

(53) The degassing compartment a is the zone located above the tray P4 up to the height of the upper edge of the weir P5. Compartment b is the zone which comprises the internal space delimited by the wall P5 of the weir and the space which occurs under the tray P4. The scrubbing compartment c is above the combination, as in the preceding alternative forms.

(54) The fluid passes from compartment a to compartment b (stream 2) by overflowing above the upper edge of the weir P5: the residence time of the fluid in the degassing compartment a is a function of the height of the weir.

(55) The surface areas for passage of the gas from compartment a and from compartment b, and the passage time of the liquid in compartments a and b, are chosen as above.

(56) The crest of the weir P4 is preferably in the form of chevrons in order to stabilize and homogenize the flow of liquid resulting from compartment a.

(57) FIG. 7 represents a functional representation of the operating principle of the separation device according to a second implementational example according to the invention: in this instance, there is no longer a scrubbing section c, and only the sections/compartments a and b: the gas streams 3 and 9 meet to form an outlet gas stream 5 and there is no longer a stream 6 from the scrubbing section c up to the stripping section b. This second example makes it possible to have a simpler design for the device and also gives very good results; even if the improvement may be lower than that introduced by the first implementational example of the invention, it remains significant.

(58) To summarize for all of these alternative forms relating to the separation device, of numerous variables, besides the choice of the sections for passage of gas and of liquid from one compartment to another, there are a certain number of other parameters which it is possible to vary in order to adjust the quality of the separation obtained: it may be a matter, in particular, of the flow rate of stripping medium injected into compartment b, or also of the choice of the temperature of the stream of the scrubbing fluid 4 in compartment c (in order to limit/control the entrainment of heavy products in the external outlet gas stream 5).

(59) In a second step, FIG. 8, which functionally represents an embodiment of the two-stage hydrocracking process integrating the separation device S described with the preceding FIGS. 1 to 7, is described: the feedstock is sent to the hydrotreating stage A: stream I the feedstock obtained at the end of stage A is sent to the liquid/solid separation S1 stage B, for example with the separator according to the alternative form illustrated in FIGS. 3a-3b: stream II the gas fraction, containing middle distillates MDs and hydrogen, obtained by the separation carried out in stage B is sent to the hydrodesulfurization stage C: stream III, with an external feedstock of gas oil type: stream IV, to form a stream V the liquid fraction, obtained by the separation carried out in stage B, is sent to the hydrocracking HCK1 stage D: stream VI, with a supply of hydrogen: H.sub.2 stream at the outlet of the hydrocracking stage D, the liquid effluent is sent to the separation S2 stage E: stream VIII at the outlet of the separation stage E, the liquid effluent is sent to the fractionation stage F: stream X at the outlet of the fractionation stage F, a cut of light products: stream XI, a petrol cut: stream XII, a cut of middle distillates MDs: stream XIII, and an unconverted liquid fraction UCO: stream XIV, are obtained the UCO fraction obtained in the fractionation stage F is sent to the hydrocracking HCK2 stage G: stream XIV the effluent (liquid/gas mixture) exiting from the hydrocracking HCK2 stage G is sent to the separation S2 stage E: stream XV the gaseous effluent obtained during the separation S2 stage E is sent to the compression stage H; it comprises hydrogen: stream IX the effluent (liquid/gas mixture) obtained at the outlet of the hydrodesulfurization stage C is sent to the separation S2 stage E: stream VII the hydrogen resulting from the compression stage H is returned at the inlet of the hydrotreating stage A, and/or of hydrodesulfurization stage C and/or of hydrocracking HCK1 stage D: H.sub.2 stream—one at least of these streams can also be replaced, in all or part, with an external supply stream of hydrogen.

(60) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(61) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(62) The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 18/53.743, filed Apr. 27, 2019, are incorporated by reference herein.

EXAMPLES

(63) The following examples illustrate the invention without limiting scope thereof.

Example 1 (Comparative)

(64) This example is a comparative example, in which the reactions for the hydrocracking of VDs or VGOs and for the hydrodesulfurization of gas oils (GOs) are carried out in a single process (cotreatment of the two feedstocks).

(65) The hydrocracking unit treats a vacuum gas oil (VGO) feedstock as a mixture with a gas oil (GO) feedstock described in Table 1:

(66) TABLE-US-00001 TABLE 1 Type VGO GO Flow rate t/h 49 51 Density t/m.sup.3 0.92 0.83 SP TBP ° C. 300 47 FP TBP ° C. 552 416 S wt % 2.18 0.68 N wtppm 1800 210
Main Operating Conditions:

(67) The mixture of the two VGO and GO feedstocks is injected into a preheating stage and then into a hydrotreating reactor R1 under the conditions set out in Table 2:

(68) TABLE-US-00002 TABLE 2 Reactor R1 Temperature ° C. 385 H.sub.2 partial pressure MPa 14 Catalyst NiMo on alumina HR1058 HSV h.sup.−1 2.60

(69) The catalyst used is a NiMo on alumina catalyst of HR1058 type sold by Axens.

(70) The effluent from this reactor is subsequently mixed with a hydrogen stream in order to be cooled and is then injected into a second “hydrocracking” reactor R2 operating under the conditions of Table 3:

(71) TABLE-US-00003 TABLE 3 Reactor R2 Temperature ° C. 390 H.sub.2 partial MPa 12.5 pressure Catalyst Metal on zeolite HYK742 HSV h.sup.−1 3.8

(72) The catalyst used is a catalyst of HYK742 type sold by Axens.

(73) R1 and R2 are the reactors in which the first stage of the hydrocracker is carried out; the effluent from R2 is subsequently sent to a separation stage composed of a chain for recovery of heat and then for high-pressure separation including a recycle compressor and making it possible to separate: on the one hand, hydrogen, hydrogen sulfide and ammonia, and, on the other hand, the effluent feeding a stripper and then an atmospheric fractionation column in order to separate streams concentrated in H.sub.2S, naphtha, kerosene, gas oil at the desired specification, and an unconverted heavy stream.

(74) This unconverted heavy stream is injected into a preheating stage and then into a hydrocracking reactor R3 in which the second hydrocracking stage is carried out. This reactor R3 is employed under the conditions set out in Table 4:

(75) TABLE-US-00004 TABLE 4 Reactor R3 Temperature ° C. 347 H.sub.2 partial MPa 12.5 pressure Catalyst Metal on amorphous silica/alumina HDK766 HSV h.sup.−1 1.4

(76) The catalyst used is a catalyst of HDK766 type sold by Axens.

(77) The effluent from R3 is subsequently injected into the high-pressure separation stage downstream of the first hydrocracking stage and recycled. The flow rate by weight at the inlet of R3 is equal to the flow rate by weight of the VGO feedstock; a bleed corresponding to 2% by weight of the flow rate of the VGO feedstock is taken at the fractionation bottom on the unconverted oil stream.

(78) The distillate cut produced in the hydrocracker and recovered from the fractionation column is in accordance with the Euro V specifications; in particular, it has less than 10 ppm by weight of sulfur.

(79) The yield of middle distillates of this process is 80% by weight, for an overall conversion of 98% by weight of the hydrocarbons having a boiling point of greater than 380° C.

(80) The total volume of catalyst necessary for this process is 112 m.sup.3.

Example 2 (Comparative)

(81) This example is a process in accordance with the invention, except in one point: a simple separator (hot drum without injection of stripping gas or of scrubbing oil) is installed in order to carry out stage B, downstream of the first hydrotreating stage A, in place of the separator device S of the invention.

(82) The feedstock I of the hydrotreating reactor R1 is a VGO identical to that treated in Example 1. The VGO feedstock is mixed with a hydrogen stream (1000 Sm.sup.3/Sm.sup.3 of VGO), then injected into a preheating stage and then into the hydrotreating reactor R1 (stage A) under the conditions set out in Table 5:

(83) TABLE-US-00005 TABLE 5 Reactor R1 in stage A Temperature ° C. 385 H.sub.2 partial pressure MPa 13 Catalyst CoMo on alumina HR1058 HSV h.sup.−1 1.67

(84) The catalyst used is a NiMo on alumina catalyst of HR1058 type sold by Axens.

(85) The effluent II from the hydrotreating reactor A is injected into a simple knockout drum (stage B). The operating conditions and degrees of recovery of this separator are given in Table 6:

(86) TABLE-US-00006 TABLE 6 Temperature ° C. 350 Pressure MPa 14 Middle distillates recovered at the bottom t/h 10 H.sub.2S + NH.sub.3 at the bottom t/h 1.5

(87) The vapour effluent III resulting from the separator in stage B is subsequently mixed with an external GO feedstock IV identical to that treated in Example 1. The hydrotreated mixture V is sent (stage C) to a hydrodesulfurization reactor R4 operating under the conditions given in Table 7:

(88) TABLE-US-00007 TABLE 7 Reactor R4 in stage C Temperature ° C. 340 H.sub.2 partial pressure MPa 12.5 Catalyst CoMo on alumina HR1058 HSV h.sup.−1 2.75

(89) The catalyst used is a NiMo on alumina catalyst of HR1058 type sold by Axens.

(90) The operating conditions of this reactor are such that the effluent XII from the fractionation stage F observes the Euro V specification (especially so that the concentration of sulfur is much less than 10 ppm by weight).

(91) The liquid effluent VI resulting from the separator used in stage B is injected into a hydrocracking reactor R2 (stage D) operating under the conditions given in Table 8:

(92) TABLE-US-00008 TABLE 8 Reactor R2 in stage D Temperature ° C. 370 H.sub.2 partial pressure MPa 12.5 Catalyst Metal on zeolite HYK742 HSV h.sup.−1 3.3

(93) The catalyst used is a metal on zeolite catalyst of HYK742 type sold by Axens.

(94) The effluents from stages C and D are subsequently sent to a separation stage E composed of a chain for recovery of heat and then for high-pressure separation including a recycle compressor (stage H) and making it possible to separate, on the one hand, hydrogen, hydrogen sulfide and ammonia and, on the other hand, the effluent feeding a stripper and then an atmospheric fractionation column (stage F) in order to separate streams concentrated in H.sub.2S, naphtha, kerosene, gas oil at the desired specification, and a heavy unconverted liquid fraction (UCO) having a boiling point of greater than 380° C. This heavy unconverted stream is injected into a preheating stage and then into a hydrocracking reactor R3 constituting the second hydrocracking stage G. This reactor is operated under the following conditions set out in Table 9.

(95) TABLE-US-00009 TABLE 9 Reactor R3 in stage G Temperature ° C. 345 H.sub.2 partial MPa 125 pressure Catalyst Metal on amorphous silica/alumina HDK766 HSV h.sup.−1 1.4

(96) The catalyst used is a metal on amorphous silica/alumina catalyst of HDK766 type sold by Axens.

(97) The effluent from R3 (stage G) is subsequently injected into the high-pressure separation stage E downstream of the first hydrocracking stage D and recycled. The flow rate by weight at the inlet of R3 is equal to the flow rate by weight of the VGO feedstock; a bleed corresponding to 1% by weight of the flow rate of the VGO feedstock is taken at the fractionation bottom on the unconverted oil stream.

(98) The produced distillate cut recovered from the fractionation column of stage F is in accordance with the Euro V specifications; in particular, it exhibits less than 10 ppm by weight of sulfur.

(99) The yield of middle distillates of this process is 82% by weight, for an overall conversion of 99% by weight of the hydrocarbons having a boiling point of greater than 380° C.

(100) The total volume of catalyst necessary for this process is 84 m.sup.3.

Example 3 (In Accordance With the Invention)

(101) This example is in accordance with the invention, with an innovative separator S installed downstream of the first hydrotreating stage A in order to carry out the separation stage B. In this example, the alternative form of separator according to FIGS. 3a-3b ?? is chosen.

(102) The feedstock I of the hydrotreating reactor R1 is a VGO identical to that treated in Example 1. The VGO feedstock is mixed with a hydrogen stream (1000 Sm.sup.3/Sm.sup.3 of VGO), then injected into a preheating stage and then into the hydrotreating reactor R1 (stage A) under the conditions set out in Table 10:

(103) TABLE-US-00010 TABLE 10 Reactor R1 in stage A Temperature ° C. 385 H.sub.2 partial pressure MPa 13 Catalyst CoMo on alumina HR1058 HSV h.sup.−1 1.67

(104) The catalyst used is a NiMo on alumina catalyst of HR1058 type sold by Axens.

(105) The effluent II from the hydrotreating reactor of stage A is injected into the innovative separator S, which makes it possible to increase the degree of recovery of the middle distillates at the top. The operating conditions and degrees of recovery of this separator S are given in Table 11:

(106) TABLE-US-00011 TABLE 11 Temperature ° C. 350 Pressure MPa 14 Scrubbing oil flow rate t/h 5 Stripping hydrogen flow rate t/h 9 Middle distillates recovered at the bottom t/h 8.0 H.sub.2S + NH.sub.3 at the bottom t/h 1.3

(107) The vapour effluent III resulting from the separator S in stage B is subsequently mixed with an external GO feedstock IV identical to that treated in Example 1. The hydrotreated mixture V is sent, for stage C, to a hydrodesulfurization reactor R4 operating under the conditions given in Table 12:

(108) TABLE-US-00012 TABLE 12 Reactor R4 in stage C Temperature ° C. 340 H.sub.2 partial pressure MPa 12.5 Catalyst CoMo on alumina HR1058 HSV h.sup.−1 2.75

(109) The catalyst used is a NiMo on alumina catalyst of HR1058 type sold by Axens.

(110) The operating conditions of this reactor are such that the effluent XII from the fractionation stage F is at the Euro V specification (in particular, the concentration of sulfur is less than 10 ppm by weight).

(111) The liquid effluent VI resulting from the separator S of stage B is injected into a hydrocracking reactor R2 (stage D) operating under the conditions given in Table 13:

(112) TABLE-US-00013 TABLE 13 Reactor R2 in stage D Temperature ° C. 370 H.sub.2 partial pressure MPa 12.5 Catalyst Metal on zeolite HYK742 HSV h.sup.−1 3.3

(113) The catalyst used is a metal on zeolite catalyst of HYK742 type sold by Axens.

(114) The effluents from stages C and D are subsequently sent to a separation stage E composed of a chain for recovery of heat and then for high-pressure separation including a recycle compressor (stage H) and making it possible to separate: on the one hand, hydrogen, hydrogen sulfide and ammonia, and, on the other hand, the effluent feeding a stripper and then an atmospheric fractionation column (stage F) in order to separate streams concentrated in H.sub.2S, naphtha, kerosene, gas oil at the desired specification, and a heavy unconverted liquid fraction (UCO) having a boiling point of greater than 380° C.

(115) This heavy unconverted stream is injected into a preheating stage and then into a hydrocracking reactor R3 constituting the second hydrocracking stage G. This reactor is operated under the following conditions set out in Table 14:

(116) TABLE-US-00014 TABLE 14 Reactor R3 in stage G Temperature ° C. 345 H.sub.2 partial MPa 125 pressure Catalyst Metal on amorphous silica/alumina HDK766 HSV h.sup.−1 1.4

(117) The catalyst used is a metal on amorphous silica/alumina catalyst of HDK766 type sold by Axens.

(118) The effluent from R3 (stage G) is subsequently injected into the high-pressure separation stage E downstream of the first hydrocracking stage D and recycled. The flow rate by weight at the inlet of R3 is equal to the flow rate by weight of the VGO feedstock; a bleed corresponding to 1% by weight of the flow rate of the VGO feedstock is taken at the fractionation bottom on the unconverted oil stream.

(119) The produced distillate cut recovered from the fractionation column is in accordance with the Euro V specifications; in particular, it has less than 10 ppm by weight of sulfur.

(120) The yield of middle distillates of this process is 83% by weight, for an overall conversion of 99% by weight of the hydrocarbons having a boiling point of greater than 380° C.

(121) In this scheme, 8 t/h of middle distillates resulting from R1 pass through R2, versus 10 t/h in Example 2, i.e. 2 t/h less. In point of fact, the middle distillates injected into the hydrocracking reactor R2 are converted into lighter products, such as petrols or gases, resulting in an overall loss in yield.

(122) The process of Example 3 thus exhibits a greater yield of middle distillates.

(123) The total volume of catalyst necessary for this scheme is 82.8 m.sup.3.

(124) Unexpectedly, the use of the innovative separator in stage B under the operating conditions set out makes it possible, in comparison with the “coprocessing” or “cotreatment” processes of Example 1: to reduce the initial capital costs and the catalyst consumption in the second hydrocracking stage G, which is reflected by a reduction in the total volume of catalyst necessary for the combined process, to limit the cracking both of the feedstock of gas oil type and of the gas oil formed in the hydrotreating stage in the hydrocracking stage, which is reflected by the increase in the yield of middle distillates, to minimize the amount of inhibitors, such as H.sub.2S and NH.sub.3, injected into the hydrocracking reactor and thus to optimize the design thereof while minimizing the amount of catalyst necessary, for an equivalent cycle time.

(125) It makes it possible, in comparison with the use of a simple separator as in Example 2: to limit even more the cracking both of the feedstock of gas oil type and of the gas oil formed in the hydrotreating stage in the hydrocracking stage, which is reflected by the increase in the yield of middle distillates.

(126) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(127) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.