FR3080544A1 - DEVICE FOR SEPARATING LIQUID AND GAS. - Google Patents

Abstract

The invention relates to a device for separating liquid and gas: said device comprises a partitioned enclosure (a, b) with the aid of at least one wall; the compartments comprise a degassing compartment (a) and a downstream compartment for stripping (b), - the degassing compartment (a) is in fluid connection with the external fluid inlet to be separated (1), and with a first gas outlet (3) and a degassed liquid outlet ( 2), - the stripping compartment (b) is in fluid connection with an inlet of said degassed liquid (2), a stripping media inlet (8), a second gas outlet (9) and a liquid outlet (7). ) - the passage of the degassed liquid (2) from the outlet of the degassing compartment (a) to the inlet of the stripping compartment (b) is ensured by an opening (x) in the wall and / or by overflow above said wall.

Description

Liquid and gas separation device

Field of the invention

The invention relates to a device for separating a fluid comprising a liquid phase and a gaseous phase into a liquid on the one hand, a gas on the other hand. Separation operations of this type are encountered in many processes in the field of chemical engineering, and very particularly in the field of refining and petrochemistry: the invention thus applies in particular to any process simultaneously involving a phase liquid consisting of a mixture of hydrocarbons, or at least one hydrocarbon, and a gaseous phase, for example a mixture of hydrogen and vapor fractions of the hydrocarbon (s) with the liquid phase. It applies in particular in the hydrotreatment, hydrocracking and hydroconversion processes of atmospheric distillate, vacuum distillate or atmospheric or vacuum residues. In all these processes, there are between the reaction stages, either between reactors or at the outlet of a reactor, separation devices, often referred to as separator flasks by their generally cylindrical / rounded shape, the function of which is is to separate the gas fractions from the liquid fractions depending, in particular, on the pressure and temperature conditions. The quality of separation of a separating device is measured in particular as the concentration (or partial flow) of light / gaseous compounds in the separated liquid phase and the concentration (or partial flow) of heavy compounds (liquids) in the gas phase separated: the lower these concentrations, the better the separation.

Prior art

There are many separator designs, including for example that described in patent EP 1 086 734, which proposes a separation with three different sections: - a primary separator for the flows of fluid to be separated, including the ratio of gas to liquid mass flow rates G / L is between 0.1 and 10 and consists of a tube terminated by at least one tangential outlet imposing on the flow a rotation of 90 °, - a secondary separator for the flows of fluid to be separated whose ratio G / L is between 10 and 20 and consists of a cyclone with free tangential entry, - and finally a system limiting the formation of liquid vortex in a third section. This separator is efficient, however it can be further improved, in particular in the case where the relative volatilities of the products to be separated are low.

The object of the invention is therefore to design an improved separation device, which is in particular more effective for separating fluids even at high pressure and / or high temperature, even when the relative volatilities of the products to be separated are low, while remaining as compact as possible.

Summary of the invention

The invention firstly relates to a device for separating liquid and gas from a fluid combining a liquid phase and a gaseous phase, such as:

said device comprises a single enclosure delimited by external walls and comprising an external fluid inlet, an external liquid outlet and an external gas outlet, the enclosure being oriented along a substantially vertical or oblique axis and being compartmentalized in at least two compartments using at least one internal wall of the enclosure and oriented substantially along said axis,

- the compartments include an upstream degassing compartment and a downstream stripping compartment,

- the upstream degassing compartment is in fluid connection with on the one hand the external inlet of fluid to be separated, with on the other hand a first gas outlet and an outlet of degassed liquid,

the stripping compartment is in fluid connection with an inlet for said degassed liquid, an inlet for stripping medium, a second gas outlet and a liquid outlet,

- the first and second gas outlets are in fluid connection with the external gas outlet of the enclosure,

- the liquid outlet of the stripping compartment is in fluid connection with the external liquid outlet of the enclosure,

- The passage of the degassed liquid from the outlet of the degassing compartment towards the entry of the stripping compartment is ensured by at least one opening made in the internal wall and / or by overflow above said internal wall separating said compartments.

The term stripping is also known by the Anglo-Saxon term "stripping". The terms "upstream" and "downstream" refer to the general flow of the fluid to be separated in the enclosure. The term "compartment" should be understood as a zone in the enclosure delimited at least partially by at least one internal wall, in particular lateral. The term "section" may also be used in this text with the same meaning.

In the invention, we therefore use a device with a single enclosure, to favor the compactness of the device as a whole.

The device of the invention uses at least two sections, including a first degassing section, where the fluid to be separated will approach its thermodynamic equilibrium, in particular in terms of temperature, with a first part of the gas contained in the fluid which is naturally separates from the fluid without mechanical or other action, unless the dimensioning of this section is adjusted appropriately according to certain parameters related to the physico-chemical characteristics of the fluid and its flow rate. It may be the dimensioning of the fluid passage section, of the passage surface of the gas extracted from the fluid, also according to the passage time of the fluid in this section referred to in this section to reach the desired degassing level.

The device then uses a stripping section, an operation consisting in treating the degassed fluid in order to vaporize the maximum of the remaining gaseous compounds, which are dissolved in the liquid phase of the fluid. The treatment consists in injecting a stripping medium, namely a gas such as hydrogen, water in the form of vapor or nitrogen, injection of gas which makes it possible to lower the partial pressure of the gases to be separated and thus to spray them. Here again, the separation efficiency obtained in this section can be adjusted by choosing an appropriate dimensioning, in particular an adequate gas passage surface which will also define the residence time of the fluid in this section.

These two successive operations, by themselves, make it possible to obtain a very effective separation of the fluid to be treated. And the delimitation of the compartments in which these operations are carried out, by adding internal wall (s) in the enclosure of the separator, is simple to implement, and, above all, makes the separator flexible by adapting the shape, sizing and arrangement of the wall (s) according to the characteristics of the fluid to be treated. This wall is in particular adaptable to adjust the transfer of the degassed fluid from the degassing compartment to the stripping compartment:

- we will be able, in particular, to adjust its relative height with respect to that of the enclosure and with respect to the level of fluid expected in the enclosure if we choose a transfer by overflow,

- we will also be able to choose the shape of the opening in the wall and / or the size and / or the number and position of the orifices, their distribution, their level on the height of the wall relative to the level of expected fluid also, if the liquid enters the stripping compartment is made through the wall through one or more orifices.

This direct transfer from one compartment to another, from one operation to another, is very advantageous, in particular in terms of limitation of the residence time of the fluid (better efficiency), in terms of limitation of pressure drop. ...

According to one embodiment, this internal wall is provided with a plurality of openings, optionally equipped with non-return valves. The presence of these valves guarantees that there is no reflux of the liquid from the stripping compartment towards the degassing compartment.

According to another embodiment, this internal wall operates by overflow and its upper edge is in the form of chevrons, which improves the stabilization and the homogenization of the flow of liquid from the degassing compartment towards the stripping compartment.

According to a variant of the invention, the external walls of the enclosure comprise lateral walls, a bottom wall and an upper wall, the internal wall being flat and coming to connect two zones of the external lateral walls of the enclosure, the upstream degassing and downstream stripping compartments each being delimited laterally on the one hand by said internal wall and on the other hand by a portion of external lateral walls on either side of said internal wall.

According to another variant, the internal wall alone delimits one of the compartments while being closed laterally, and is in particular arranged concentrically around the axis of the enclosure. In this case, preferably, the enclosure has essentially cylindrical lateral external walls, and the internal wall is concentric with said cylindrical walls, with the upstream degassing compartment arranged outermost and of annular shape, and the downstream stripping compartment arranged inside the internal wall, or vice versa.

According to a particular configuration of this other variant, the internal wall extends at the bottom towards the external lateral walls of the enclosure by a solid plate, said wall acting as a weir. Above the plate, the external fluid inlet is arranged, the degassing compartment being delimited by the internal wall and the external wall of the enclosure laterally and by the plate in the lower part, the stripping compartment being delimited by the internal portion of the internal wall and the enclosure area located under the solid tray of the degassing compartment. Unlike previous configurations, in this case, the two compartments are substantially superimposed on each other, and not joined sideways to each other.

According to a preferred optional embodiment, the enclosure according to the invention comprises a third so-called washing compartment, downstream of the first two compartments, and disposed above them in the enclosure. This washing compartment is advantageously provided on the one hand with an external washing fluid inlet, with a first gas inlet in fluid connection with the first gas outlet of the first degassing compartment and with a second gas inlet in connection fluid with the second gas outlet from the second stripping compartment, and on the other hand with a liquid outlet in fluid connection with the second stripping compartment and with a gas outlet in fluid connection with the external gas outlet of the enclosure.

The washing fluid can be composed of hydrocarbons: preferably a light or heavier cut essence (LVGO, HVGO), or a deasphalted oil or a cut of medium distillates (diesel or kerosene), a naphtha, a aromatic oil from catalytic cracking. This fluid can moreover come from the installation where the separation device according to the invention is placed, for example it can come from a vacuum distillation operation in a hydrocracking process or be an external charge, which will then be treated in a reactor arranged downstream of the separation device of the invention.

In this washing compartment, there is preferably a counter-current contact between a descending liquid phase and an essentially rising gas phase. Preferably, the washing compartment comprises a tray for dispensing the washing fluid, and optionally a racking tray.

In the case where a washing compartment is provided, it is advantageously provided that the internal wall oriented substantially vertically is surmounted, perpendicular to its upper edge, by an inclined plate joining the lateral external wall of the enclosure so covering the first degassing compartment disposed between the internal wall and the lateral external wall and directing the liquid leaving the liquid outlet of the washing compartment directly above said first degassing compartment towards an inlet of the second stripping compartment. In this configuration, this prevents liquid from the washing compartment from returning to the degassing compartment.

Still in the case where a washing compartment is provided, in the configuration where the internal wall alone delimits the first degassing compartment, it is advantageously surmounted above its upper edge by a sloping roof, so covering the first degassing compartment and directing the liquid leaving the liquid outlet of the washing compartment directly above said first compartment towards an inlet of the second stripping compartment disposed between said internal wall and the external side wall of the pregnant. Again, if the degassing compartment is "in the middle" of the enclosure, this roof prevents any liquid from the washing compartment from returning to the degassing compartment.

In general therefore, whatever the relative configuration of the degassing and stripping compartment, the washing compartment is located above them, and it is advisable to provide any deflector means to prevent or limit the return of liquid from the washing compartment to the degassing compartment.

The invention also relates to any method of implementing the device described above, and such that the following successive steps are carried out:

a degassing step of the fluid to be separated in the liquid phase and in the gaseous phase by approaching the fluid to its thermodynamic equilibrium in the first degassing compartment,

- a stripping step by injecting a stripping medium to vaporize at least part of the light components dissolved in the liquid obtained by the degassing step in the stripping compartment,

- optionally a washing step by injecting washing media to condense the heavy compounds from the degassing and / or stripping step in the washing compartment.

Advantageously, it is possible to separate by this process in the liquid phase and in the gaseous phase a fluid having a gas mass flow rate on liquid G / L of between 0.1 and 10, and preferably between 0.5 and 2. This process applies therefore a very wide range of fluids.

Advantageously, the temperature of the fluid to be separated by this process can be between 20 and 600 ° C, and preferably between 150 and 450 ° C. the process therefore applies to both ambient temperatures and high temperatures.

Advantageously, the pressure of the fluid to be separated by this process can be between 0.1 and 25 MPa, in particular between 15 and 20 MPa. Here again, the process thus applies to both relatively low fluid pressures and very high pressures.

Advantageously, the passage time of the fluid in the degassing compartment and / or in the stripping compartment is between 30 seconds and 10 minutes, which makes the total residence time of the fluid in the compartment reasonable from an industrial point of view.

Preferably, the section for passage of the fluid in the degassing compartment and / or in the stripping compartment, and / or in the washing compartment when it is present, is chosen to be sufficient to limit the speed of the gas below the speed. critical droplet drive, preferably below 90% or below 80% of said critical speed.

Recall that the critical speed v _c can be calculated, in a known manner, using the following formula, with d | the density of the liquid phase, and d _g the density of the gas phase of the fluid:

The invention also relates to the use of the device described above or of the process described above to separate a liquid phase consisting of a mixture of a liquid of hydrocarbons or at least one hydrocarbon, and of a gaseous phase. consisting of a mixture of hydrogen and vapor fractions of said hydrocarbon (s), from a fluid comprising this mixture, in particular during a hydrotreatment process of heavy or light hydrocarbon charges such as a process of hydrodesulfurization, hydrodenitrogenation, hydrodearomatization, or during a hydrocracking process.

detailed description

The invention will be detailed below with the aid of nonlimiting examples illustrated by the following figures:

Figure 1: a functional representation of the operating principle of the separation device according to a first example according to the invention,

FIGS. 2a, 2b: a first variant of the separation device according to the invention, respectively in a vertical section and a horizontal section at mid-height according to the first example according to the invention,

FIGS. 3a, 3b: a second variant of the separation device according to the invention, respectively in a vertical section and a horizontal section at mid-height, according to the first example according to the invention,

FIGS. 4a, 4b: a third variant of the separation device according to the invention, respectively in a vertical section and a horizontal section at mid-height, according to the first example according to the invention,

FIG. 5: a fourth variant of the separation device according to the invention in a vertical section, according to the first example according to the invention,

Figure 6: the first variant of Figures 2a, 2b in a perspective view with the representation of fluid flows in the device; according to the first example according to the invention,

Figure 7: a functional representation of the operating principle of the separation device according to a second example according to the invention.

The figures are schematic and the different elements shown are not necessarily to scale. The separation device according to the invention, also designated by the term separator, defines an enclosure the largest dimension of which is arranged along a vertical axis X in its operating position, and this is how it is represented in the figures . Identical components / with the same meaning keep the same reference from one figure to another.

Figure 1 is therefore a functional representation of the gas / liquid separation operated by the separator according to the invention. Let us take the example of a fluid in the form of a two-phase liquid / vapor flow whose ratio of gas mass flow rates to liquid G / L 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 flow to be separated is between 0.1 and 25 MPa, preferably between 15 and 20 MPa. The flow to be separated is for example the effluent from a hydrotreating reactor in a fixed bed, or the effluent from a hydrocracking reactor in a fixed bed.

The separation according to the invention is made in three sections (also called compartments in the description which follows of the different separator variants): a degassing section a, a stripping section b, and an optional section c wash. These two or three sections are according to the invention integrated in the same separator, in a single enclosure therefore.

The entire separator operates at the same pressure, or substantially the same pressure as that of the two-phase incoming flow 1 to be separated.

The flow to be separated 1 is injected into the degassing section a. The purpose of this operation is to perform a first separation, by letting the fluid reach or approach its thermodynamic equilibrium, in temperature and in pressure. It is then possible to withdraw from the section a predominantly liquid flow 2, called degassed liquid, and a predominantly gaseous flow 3.

To ensure that this first separation takes place effectively, the degassing section a is dimensioned so as to limit the entrainment of liquid droplets in the flow 3: the passage surface of the gas flow 3 in the section a is chosen. sufficient to limit the speed of the gas below the critical speed for driving the droplets, preferably below 90% of this speed, even more preferably below 80% of this critical speed. The critical speed is defined as the rate of drop of droplets of 100 micrometers in diameter in the gas flow under the operating conditions of section a.

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

In zone a, there is thus a lower zone in which, in operation, there is a continuous liquid phase and an upper zone in which there is a continuous gaseous phase. These two phases are delimited from each other by an interface, which will define the level of liquid in this area. The predominantly liquid stream 2 leaving section a is then injected into the stripping section b. The purpose of this operation is to vaporize part of the light / gaseous components in the degassed liquid 2. To carry out the stripping, a stream 8 of a stripping medium is injected in section b, this medium here being hydrogen. : injecting hydrogen lowers the partial pressure of the gases (hydrocarbons) to be separated and vaporizes them. Section b can optionally be provided with rafters, trays (such as “shower decks”, “dises” and “donuts” according to English terminology, with caps, flaps or any other distillation tray technology known to the skilled in the art).

Alternatively, other gases than hydrogen can be chosen as the stripping medium, such as a light gas such as water vapor or nitrogen.

The gas passage surface in section b is sufficient to limit the speed of the gas below the critical droplet drive speed, preferably below 90% of this speed, even more preferably below 80% of this speed. critical speed. The passage time of the liquid in section b is between 30 seconds and 10 minutes.

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

The gas flow 3 from step a is injected with the gas flow 9 from section b in the washing section c. This washing step is optional. It makes it possible to reduce the quantity of heavy compounds entrained in the gas flow 5 which leaves the separator. The objective of this step is to condense the heavy compounds from section a and, to a lesser extent, from section b. It also makes it possible to recover the droplets of liquids entrained from these sections.

A stream 4 of a washing media is injected into section c to absorb these heavy compounds. This washing media can be composed of hydrocarbons. Preferably, this flow is a light or heavy vacuum diesel fuel (known by their acronyms LVGO and HVGO), a deasphalted oil (DAO) or a cut of medium distillates (diesel or kerosene), a naphtha, an aromatic oil derived from catalytic cracking (LCO / HCO). The washing flow can come from the process where the separator is installed or imported, for example from a vacuum distillation installed in the hydrocracking process concerned. It can also be an external charge which is then treated in reactors installed downstream of the separator, on its gas outlet or on its liquid outlet.

In this washing section c, there is a counter-current contact between a descending liquid phase and an essentially gaseous rising phase, according to a technology known to those skilled in the art.

Section c is preferably provided with structured or bulk packing, preferably structured, maximizing the liquid / vapor exchanges. Section c can also be composed of rafters, trays such as ("shower decks", "dise" & donuts "), clamshell or any other distillation tray technology known to those skilled in the art.

Note that if section b and section c can both be fitted with linings, also called internal, such as those mentioned above, they remain distinct from each other, the input / output flows passing through them being different: the flow which crosses zone c is predominantly, in particular essentially, gaseous, which contains liquid dispersed within it, while zone b is crossed by a flow predominantly, in particular essentially, liquid with gas dispersed within it .

The passage area of the gas from section c is sufficient to limit the speed of the gas below the critical speed for driving the droplets, preferably below 90% of this speed, even more preferably below 80% of this critical speed.

Optionally, a mattress called "coalescer" (or "mesh" according to the English term or even coalescer in French) is installed in the upper part of section c, in order to coalesce the entrained droplets, to increase the diameter of these droplets and limit their entrainment in the gas.

The flow on the linings is of the trickling type (the continuous phase is here the gas phase).

In the case where the washing medium is liquid under the operating conditions, the washing oil absorbs part of the hydrocarbons from sections a and c and makes it possible to avoid the export of droplets in the gas flow leaving the separator. This makes it possible to increase the speed of the gases in section a, and therefore to limit the passage surface thereof. Limiting the export of droplets in the gas flow 5 is advantageous for the equipment disposed downstream of the separator, because it limits the composition fluctuations and possibly the fouling of this equipment.

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

The temperature of the wash media stream 4 is preferably lower than the temperature of the stream 1 entering the degassing section a, in order to maximize the condensation phenomenon of the heavy vapors and thus limit the flow rate. The temperature of flow 4 can be controlled by a heat exchanger upstream of injection into the separator.

The temperature of stream 1 is advantageously between 20 and 600 ° C, and preferably between 150 and 450 ° C. The temperature of stream 4 is advantageously also between 20 and 600 ° C., the same range as for stream 1 therefore. But preferably, the temperature of stream 4 is chosen to be 50 ° C cooler than the temperature of stream 1, and even more preferably 100 ° C cooler than the temperature of stream 1.

The flow rate of stream 4 is chosen to be sufficient to obtain wetting of the packing or of the plates used in section c.

The flow of liquid 6 from the washing section c is also injected into the stripping section b. This flow is composed of the condensed compounds in section c and the washing medium of the non-vaporized flow 4.

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

The temperature of the stripping section b is the thermodynamic equilibrium temperature of the mixture of flows 2, 6 and 8, it is generally lower than the temperature of the degassing section a of a few degrees.

In summary, the different exchanges / transfers of flows in the three sections of the separator are therefore the following:

the fluid to be separated 1 enters from the outside of the separator into the degassing section a it leaves the section has a liquid 2 degassed towards the stripping section b it leaves the section has a gas 3 which goes to the washing section c the degassed liquid 2 enters the stripping section b a stripping medium 8 enters the stripping section b a gas 9 leaves the stripping section towards the washing section c and a liquid 7 towards the outside of the separator in the washing section, enter the gas 3 coming from the degassing section a, the gas 9 coming from the stripping section b, the washing media 4 exit from the washing section c, a flow of liquid 6 towards the stripping b, and a gas flow 5 towards the outside of the separator.

Overall, there is therefore a two-phase liquid / gas incoming flow 1 in the separator through the degassing section a, a liquid flow 7 leaving through the stripping section b and a gas flow 5 leaving through the washing section c.

The different variants of the separator design implementing this separation process are described one by one. In all the variants represented in FIGS. 2 to 6, the separator S has a single enclosure of substantially cylindrical side walls, with a bottom wall and an upper wall, both slightly rounded / convex / which can therefore have a hemispherical or hemispherical shape. elliptical. This shape makes it possible to designate this type of enclosure also under the term of "separating balloon". The separator, in the operating position, is oriented along the X axis of the cylindrical walls, here vertical axis. Naturally, the invention applies in the same way to dividers whose section is not cylindrical or which is oriented obliquely to the vertical, as well as to dividers whose bottom wall and / or the upper wall is not rounded but flat for example.

According to Figures 2a and 2b and 6, a first variant of separator S is shown with its side walls L cylindrical. An internal wall P1 is arranged inside the enclosure: it is a flat wall and oriented vertically. In the lower part, it rests on the bottom wall of the enclosure, and its upper edge bs corresponds approximately between half and 2/3 of the height H of the cylindrical side walls L of the enclosure. This wall P1 joins by its two lateral edges the lateral wall of the enclosure, and thus defines two coaxial compartments: the compartment a for degassing and the compartment b for stripping. Compartment a is provided with the inlet 1 for the fluid to be separated

In the upper part, above the upper edge bs of the internal wall P1, is the washing compartment c, as shown in FIG. 6.

The wall P1, as also shown in FIG. 6, is provided with through x orifices and distributed over a strip of height h: the position, the size, the distribution of these orifices are chosen so as to allow the degassed liquid 3 to pass compartment a towards compartment b, maintaining the fluid 1 for a sufficient residence time in the degassing compartment. The liquid passage surface of all the orifices x is such that the liquid flow 3 which passes through them is at least equal to the liquid flow coming from the flow 1. Optionally, the orifices x, or at least some of them, are fitted with non-return valves (not shown) to minimize the recirculation of liquid from compartment b to compartment a.

Alternatively, a wall P1 is kept full and the degassed liquid 3 is transferred from compartment a to compartment b by overflow of the liquid over the upper edge bs of the internal wall P1, which forms a spillway. 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 is fitted, acting as a weir, rafters, so to stabilize and homogenize the flow of liquid from compartment a to compartment b.

The upper edge bs of the internal wall P1 is surmounted by a wall d, shown in FIG. 6, which is a wall arranged above, from the upper edge bs to the side walls L of the enclosure. It is preferably without contact with the upper edge for mechanical reasons, but it is also possible to provide continuity between the upper edge bs and this wall d. This wall d is obliquely oriented towards the center of the enclosure in the form of an inclined plate which separates compartment a from compartment c for washing. This inclined plate is optionally provided with valves and / or caps in order to let the gas coming from compartment a pass to compartment c, but avoiding the passage of liquid from compartment c to compartment a. Preferably, the inclined plate d is not in contact with the internal partition wall P1 between a and b. The angle of inclination of the plate d relative to the horizontal is between 1 ° and 45 °, preferably between 5 ° and 30 °. Here, as an example, it is around 20 °.

The surface area for the passage of gas from compartment a to compartment c via flow 3 is chosen to be sufficient to limit the speed of the gas below the critical speed of droplet entrainment, preferably below 90% of this speed, again more preferably below 80% of this critical speed.

The passage time of the liquid in the stripping compartment b is between 30 seconds and 10 minutes. The stripping medium (flow 8) is injected into compartment b through a diffuser. The liquid withdrawal orifice (flow 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 conduit discharging the liquid from the compartment. These can be, for example, braces.

When the washing compartment c exists, as is the case shown in FIGS. 2 and 6, then the washing oil is injected into the compartment c via a distributor plate (not shown) ensuring a homogeneous distribution over the internals of the compartment c, which is preferably provided with structured or bulk packing, preferably structured, maximizing the liquid / vapor exchanges.

Compartment c can also include chevrons, trays such as “shower decks, dise & donuts”, clamshell or any other conventional distillation tray technology.

The gas passage surface (flow 5) from compartment c is chosen to be sufficient to limit the speed of the gas below the critical speed for driving the droplets, preferably below 90% of this speed, even more preferably below 80% of this critical speed.

Figures 3a and 3b describe a second variant of separator S. Will only be described which differs from the first variant described above. The main difference is the modification in the relative configuration between compartments a and b: Here they are arranged concentric to the vertical axis of the separator, by an internal wall P2 which defines a cylinder placed on the bottom wall of the separator and centered on the vertical axis thereof: 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 truncated cone whose smallest base surmounting the cylindrical upper edge, with or without continuity, of the wall P2, and whose base the larger joins the outer side walls L of the separator.

Figures 4a and 4b describe a third variant of separator S. Will be described, for this variant, that which differs from the second variant described above. In this variant, the two compartments a and b are arranged concentrically as in the second variant, but this time it is the compartment b which is of annular shape and which is arranged outside, and the compartment a which is delimited by the cylindrical interior space delimited by the internal wall P3. The inclined wall d3 separating the compartment a from the upper washing compartment c this time has the shape of a conical roof coming to overcome at a certain distance the upper edge bs of the wall P3 by presenting at its base a diameter slightly greater than that of the wall P3. The gas (flow 3) can thus circulate as shown from compartment a towards compartment c by flowing upwards between the upper edge of the wall P3 and the base of the roof d3.

FIG. 5 is a fourth variant of a separator, where the separation between the compartments a and b is done using a solid plate P4 disposed substantially horizontally in the enclosure and of annular and full shape, and provided with a weir constituted by the circular central opening of the solid plate extending upwards into a portion of solid cylindrical wall P4 over a given height. The injection of the flow 1 of fluid to be treated is done above the plate P4. In the upper part of the weir P5, above its upper edge, is arranged a conical roof d3 of the same design as that used in the previous variant.

The degassing compartment a is the area above the tray P4 up to the height of the upper edge of the weir P5. The compartment b is the zone which includes the internal space delimited by the wall P5 of the weir and the space which is under the plate P4. The washing compartment c is above the assembly, as in the previous variants.

The fluid passes from compartment a to compartment b (flow 2) overflowing above the upper edge of the weir P5: the residence time of the fluid in the degassing compartment a depends on the height of the weir.

The gas passage surfaces from compartment a and from compartment b, and the time of passage of the liquid in compartments a and b are chosen as above.

The edge of the weir P4 is preferably in the form of chevrons in order to stabilize and homogenize the flow of liquid from compartment a.

FIG. 7 represents a functional representation of the operating principle of the separation device according to a second exemplary embodiment according to the invention: here there is no longer a washing section c, and only the sections / compartments a and b: the stream 3 and 9 of gas meet to form an outlet gas stream 5, there is no longer a stream 6 from the washing section c to the stripping section b. This second example makes it possible to have a simpler device design, and also gives very good results, even if the improvement may be less than that provided by the first embodiment of the invention, it remains significant.

In summary for all of these variants, many variables, in addition to the choice of gas and liquid passage sections from one compartment to another, we have a certain number of other parameters on which we can play to adjust the quality of the separation obtained: it may be, in particular, the flow rate of stripping media injected into compartment b, or else the choice of the temperature of the flow of washing fluid 4 in compartment c (to limit / control the heavy driving in the external gas outlet stream 5.

Examples of Application of the Invention

Example 1 non-compliant: it uses a simple separator (“balloon I”), that is to say a separator using an enclosure of substantially cylindrical shape but just equipped with a coalescing mattress, with an inlet for fluid to be treated, a gas outlet and a liquid outlet, without any compartmentalization in the enclosure.

Table 1 below gives the main characteristics of the charge (of the fluid) to be separated in the liquid phase and in the solid phase.

Table 1

ç _TO , Total mass flow kg / h 214592 T, Temperature ° C 350 P, Pressure bar 145 MM, Molar mass g / tnol 19.25 Fraction sprayed at thermodynamic balance % weight 23.70% Composition in light kg / h 26578 , h ₃ kg / h 21000 h. _2s kg / h 4421.61 m _a kg / h 410.54 vs\ kg / h 140.22 _it's kg / h 183.22 G kg / h 193.89 kg / h 229.20

TBP Weight (%) T (° C) 1 115.29 5 233.74 10 296.04 30 383.29 50 417.67 70 444.78 90 487.57 95 511.16 98 536.18

The composition "TBP" is the boiling curve of the heavy fraction, it reads as follows: 1% end under 115.29 °, 70% end under 444.78 ° ....

The separator flask is a simple vertical flask provided with a horizontal coalescing mattress in its upper part and an anti-vortex on its liquid outlet. Its diameter is calculated to limit the entrainment of droplets whose representative size is assumed to be 200 micrometers. By representative size is meant the value of the diameter above which the diameter of 99% of the droplets is situated. It is assumed that training is avoided in the following two cases:

1) Absence of a coalescing mattress: the ascending speed of the gas is equal to (or less) 80% of the critical speed (speed of fall of the droplets);

2) Presence of a coalescing mattress: the ascending speed of the gas is equal to (or lower) 170% of the critical speed The droplets are collected for the coalescer.

The critical speed is calculated using the formula which was recalled at the beginning of this text.

The flask is dimensioned so that the liquid residence time is 2 minutes. These criteria, as well as the conventional manufacturing constraints, allow the following geometry to be calculated:

Table 2:

Liquid inlet flow Q „, mass flow d _L , density of the liquid volumetric flow fcff / m ³ " ³ W 163672 670.50 244.1 Steam inlet flow g®, volumetric flow 4058.1 d _R , vapor density kg / wi ³ 12.55

Sizing parameters

i? _c , critical speed m / s 0348 v _G , gas speed (target) * from 1¾ 170% m / s 0591 passage surface 1.91 t, residence time mm 2.00

Geometric characteristics of the balloon

D, diameter ml 1.56 H, height ml 4.27

A thermodynamic simulation of the separation flask was carried out. This simulation is equivalent to that carried out in the degassing compartment a of the separator according to the invention, which aims at the separation between the middle distillais and the heavy cut (380 ° C. +), therefore without injection of stripping fluid. The respective results are shown below.

Table 3: Yields of the simple separation flask.

Stream (ton / fc) Charge Head Background light 26.58 26.12 0.46 Naphtha (C5-145 ° C) 2.79 2.44 0.35 Kerosene (145-220 ° C) 4.88 3.55 1.33 Diesel (220-380 ° C) 40.33 11.81 28.53 Heavy (380 ° C +) 140.01 7.00 133.00 Total 214.59 50.92 163.68

Example 2 non-compliant: it uses a simple separator balloon ("Balloon II") provided with a coalescing mattress like Example 1 non-compliant, but this time with, in addition, H ₂ injection. In this case, we study the influence of the hydrogen injection in a separation flask with a geometry similar to that of the previous example. The incoming fluxes and composition to be separated from the process are identical to those in Example 1 The quantity of hydrogen to be injected in addition into the flask, corresponds to approximately 3% of the charge, ie 6 ton / h.

Considering the same sizing criteria, taking into account the new data, the following geometry has been established:

Table 4:

Liquid inlet flow in the feed

from process 1 mass flow kg / h 159235 d _L , density of the liquid kg / wi ⁹ 673.10 Qj ,, volumetric flow Wl® / TO 236.6

Steam input flow (in the feed from the process and addition of hydrogen

in the balloon) Q®, volumetric flow rate d _R , vapor density kg 5206.4 11.79 Sizing parameters critical speed m / s 0.360 v _E , gas speed (target) % of 1¾. 170% wi / s 0611 passage surface or* 2.37 t, residence time mm 2.00

Geometric characteristics of the balloon

B, diameter 1.74 H, height "1 3.33

A representative thermodynamic simulation of the balloon was carried out. The results of this simulation are given in the table below:

Table 5: Yields of the simple separation flask, with H ₂ injection.

Stream (ton / ft) Charge + h ₂ added Head Background light 32.58 32.18 0.40 Naphtha (C5-145 ° C) 3.17 2.51 0.28 Kerosene (145-220 ° C) 4.50 3.75 1.13

Diesel (220-380 ° C) Heavy (380 ° C +) 40.33 13.17 27.16 140.01 7.90 132.11 Total 220.59 59.50 161.09

Example 3 according to the invention:

In this example, a separator (“balloon III”) is used according to the second variant illustrated in FIGS. 3a-3b. The same load data as in non-compliant example 1 was used. The amount of hydrogen injected was calculated on 3% of the charge as in non-compliant example 2 (6 tonnes / h).

The dimensioning of the separator was carried out so as to comply with the rules of the critical velocity 10 of each section.

Central stripping compartment:

Table 6: Dimensioning of compartment b

Liquid inlet flow flow 2 mass flow kg / h 160 767

d _t , density of the volume flow liquid M ³ /! 684.5 234.9 Steam inlet flow Q%, volumetric flow n / h 1138.0 d. _e , vapor density kff / 'wi ⁵ 9.72

Liquid withdrawal in compartment b

stream 9 critical speed m / s 0400 gas speed (target) % of 1¾. 170% m / s 0680 4 ,, passage surface W ² ' 0.46 O, minimum diameter 0.77

Steam disengagement in compartment b

flow 7 d _fe , bubble diameter mm v _c , critical speed m / s 1.00 0.0792

4 _S , passage surface m ^z 0.82

D, minimum diameter m 1.02

It is understood by steam disengagement that steam in the form of bubbles could come out with the liquid in the flow 7. The passage section is therefore adapted to avoid the entrainment of bubbles downwards.

In compartment b, the choice of sizing is based on two constraints:

• entrainment of liquid at the head must be avoided • entrainment of gas at the bottom of the flask must also be avoided.

The final diameter will be the highest which meets these two criteria at the same time with these two criteria. These assumptions lead to the following dimensioning:

Geometric characteristics of the balloon

D _t , total diameter of the tank 4 ,, total passage area of the tank 1.90 2.84 Section a) deducted l _c crown width in 0.44 Q®, volumetric gas flow in a) my 4058.1 Æ ,, passage surface m ² 2.01 i? _G , gas speed wi / .s 0.560 d _L , density of the liquid in a) kg / wi ^s 670.5 d _G , vapor density in a) ftg / wi ³ 12.55 i? _c , critical speed m / s 0348 % of actual critical speed % 161

The speed of the ascending gas is less than 170% of the actual critical speed, making it possible to avoid entrainment of droplets at the head. Furthermore, the speed of the liquid is low enough not to entrain gas in the bottom.

The same constraint on the liquid entrainment is respected in the washing compartment c under the packing.

Table 7:

Calculation under mesh at the head

Liquid inlet flow 1

mass flow kg / h 1500 d _A , density of the liquid KFF / wé 823.6 HC + steam inlet flow stripping volumetric flow "'/AT 5186 d _c , vapor density ks / wi ³ 11.82 Under the packing critical speed wi / s 0398 1¾. gas speed (target) % of t ?. 170% m / s 0676 D, diameter Wis. 1.90 Aj, passage surface m ² 2.84 v _G , gas speed m / s 0508

% of critical speed% 128

The height of the liquid in the bottom zone of compartments a and b is calculated by assuming a residence time of two minutes. The compartments a and b both participate in the achievement 5 of this residence time. The number of holes x in the internal partition wall P2 between compartments a and b was calculated by choosing circular holes with a diameter of 1 inch per hole.

TABLE 8: Sizing of the bottom area: compartments a + b

Bottom area under the interface in compartments a and b

B, diameter m 1.90 passage surface Ml ² 2.84 qJ, total volumetric flow wi ^s / A 236.7 t, residence time min 2.00 h ,, liquid height 2.78

Number of holes pipe size in flow 7 balloon background inch 10 Hole diameter inch 1 number of holes 100

A thermodynamic simulation representative of the balloon according to this example 3 was carried out.

In accordance with the invention, hydrogen and washing oil are injected in the following contions:

• H ₂ : 6 ton / h at 300 ° C (as in Example 2 non-compliant) • Washing oil: 1.5 ton / h at 200 ° C

The performance results are shown below:

Table 9: Balloon yields according to example 3

Fluid to be treated (ton / ft) Charge + H2 added Head Background light 26.58 32.32 0.26 Naphtha (C5-145 ° C) 3.17 2.66 0.13 Kerosene (145-220 ° C) 4.50 4.08 0.80 Diesel (220-380 ° C) 40.33 13.97 26.36 Heavy (380 ° C +) 140.01 8.29 133.22 Total 214.59 61.33 160.77

The following table indicates the difference (“Delta”) in the flow rates of the distillaries at the top of the balloon according to example 3 of the invention (called Ballon III), compared to the first two examples (Ballon I: according to example 1 and Balloon II, according to Example 2).

Table 10: Delta Balloon I - Balloon II Balloon l-Balloon III Balloon II - Balloon III MD gain (ton / h)% recovery 1.57 2.70 1.14 5% 9% 4%

The simple balloon with hydrogen injection (Balloon II) allows a recovery of 5% compared to the single balloon (Balloon I). But the balloon according to the invention (balloon III) allows a recovery of 9%, therefore an increase of 5 points compared to non-conforming example 2.

“MD” in the table above means “Middle distillât” in English, or middle distillât in French, which corresponds to the diesel and kerosene fractions.

It can be seen from this table that the fact of using balloon III according to the invention makes it possible to recover 1.14 t / h of diesel and kerosene in addition in the overhead fraction relative to balloon II which does not conform to II, which, 5 compared to the amount of diesel and kerosene which is already recovered at the top, makes an increase in recovery of 4%.

Claims (15)

1. Device for separating (S) liquid and gas from a fluid combining a liquid phase and a gaseous phase, characterized in that: said device comprises a single enclosure delimited by external walls and comprising an external fluid inlet (1), an external liquid outlet (7) and an external gas outlet (5), the enclosure being oriented along a substantially vertical axis or oblique and being compartmentalized into at least two compartments (a, b) by means of at least one wall internal to the enclosure (P1, P2, P3, P5) and oriented substantially along said axis, - the compartments include an upstream degassing compartment (a) and a downstream stripping compartment (b), - the degassing compartment (a) is in fluid connection with on the one hand the external inlet of fluid to be separated (1), on the other hand a first gas outlet (3) and an outlet of degassed liquid (2 ) the stripping compartment (b) is in fluid connection with an inlet of said degassed liquid (2), an inlet of stripping medium (8), a second gas outlet (9) and a liquid outlet (7), - the first and second gas outlets (3,9) are in fluid connection with the external gas outlet (5) of the enclosure, - the liquid outlet of the stripping compartment (7) is in fluid connection with the external liquid outlet of the enclosure, - the passage of the degassed liquid (2) from the outlet of the degassing compartment (a) towards the inlet of the stripping compartment (b) is ensured by at least one opening (x) made in the internal wall (P1, P2, P3) and / or by overflow above said internal wall (P1) separating said compartments. 2. Device according to the preceding claim, characterized in that the internal wall (P1, P2, P3) is provided with a plurality of openings (x), optionally equipped with non-return valves. 3. Device according to claim 1, characterized in that the internal wall (P5) operates by overflow and in that its upper edge is in the form of rafters. 4. Device according to one of the preceding claims, characterized in that the external walls of the enclosure comprise lateral walls (L), a bottom wall and an upper wall, the internal wall (P1), preferably planar, coming to connect two zones of the external lateral walls (L) of the enclosure, the upstream degassing (a) and downstream stripping (b) compartments each being delimited laterally on the one hand by said internal wall and on the other hand by a portion of external side walls on either side of said internal wall. 5. Device according to one of claims 1 to 3, characterized in that the internal wall (P2, P3) alone delimits one of the compartments (a, b) being closed laterally, and is in particular arranged concentrically around of the axis of the enclosure. 6. Device according to the preceding claim, characterized in that the enclosure has essentially cylindrical lateral external walls, and in that the internal wall (P2, P3) is concentric with said cylindrical walls, with the upstream degassing compartment (a) most outwardly arranged and annular in shape, and the downstream stripping compartment (b) disposed inside the internal wall, or vice versa. 7. Device according to claim 5, characterized in that the internal wall (P5) extends in the lower part towards the external lateral walls of the enclosure by a solid plate (P4) in the form of a weir, plate above of which is disposed the external fluid inlet (1), the degassing compartment (a) being delimited by the internal wall (P5) and the external wall (L) of the enclosure laterally and by the plate (P4) in part lower, the stripping compartment (b) being delimited by the internal portion of the internal wall (P5) and the zone of the enclosure situated under the solid plate (P4) of the degassing compartment (a). 8. Device according to one of the preceding claims, characterized in that the enclosure comprises a third washing compartment (c), downstream of the first two compartments (a, b), and disposed above them in the enclosure, optionally including a coalescing mattress. 9. Device according to the preceding claim, characterized in that the washing compartment (c) is provided on the one hand with an external inlet for washing fluid (4), with a first gas inlet in fluid connection with the first outlet gas (3) from the first degassing compartment (a) and a second gas inlet in fluid connection with the second gas outlet (9) coming from the second stripping compartment (b), and on the other hand from a liquid outlet (6) in fluid connection with the second stripping compartment (b) and a gas outlet (5) in fluid connection with the external gas outlet of the enclosure. 10. Device according to claim 8 or 9, characterized in that the washing compartment (c) comprises a tray for dispensing the washing fluid, and optionally a racking tray. 11. Device according to one of claims 8 to 10, characterized in that the internal wall (P1, P2) is oriented substantially vertically and is surmounted, vertically above its upper edge (bs), by an inclined plate ( d) joining the lateral external wall (L) of the enclosure so as to cover the first degassing compartment (a) disposed between the internal wall and the lateral external wall and to direct the liquid leaving the liquid outlet of the compartment washing (c) directly above said first degassing compartment (a) towards an inlet of the second stripping compartment (b). 12. Device according to one of claims 8 to 10, characterized in that the internal wall alone delimits the first degassing compartment (P3) and in that it is surmounted, above its upper edge, by a roof steep (d3), so as to cover the first degassing compartment (a) and to direct the liquid leaving the liquid outlet of the washing compartment (c) directly above said first compartment towards an inlet of the second stripping compartment (b) disposed between said internal wall and the external lateral wall (L) of the enclosure. 13. Method for implementing the device according to one of claims 1 to 12, characterized in that the following successive steps are carried out: a step for degassing the fluid to be separated in the liquid phase and in the gaseous phase by bringing the fluid to its thermodynamic equilibrium in the first degassing compartment (a), a stripping step by injecting a stripping medium to vaporize at least part of the light components dissolved in the liquid obtained by the degassing step in the stripping compartment (b), - optionally a washing step by injecting a washing medium to condense the heavy compounds from the degassing and / or stripping step in the washing compartment (c). 14. Method according to the preceding claim, characterized in that the fluid passage section in the degassing compartment (a) and / or in the stripping compartment (b), and / or in the washing compartment (c) when it is present, is chosen to be sufficient to limit the speed of the gas below the critical speed for driving the droplets, preferably below 90% or below 80% of said critical speed. 15. Use of the device (S) according to one of claims 1 to 12 or of the method according to one of claims 13 or 14 for separating a liquid phase consisting of a mixture of a liquid of hydrocarbons or of at least one hydrocarbon, and a gaseous phase consisting of a mixture of hydrogen and vapor fractions of said hydrocarbon (s), from a fluid comprising this mixture, in particular during a hydrotreatment process of feedstocks heavy or light hydrocarbons such as a hydrodesulfurization process, hydrodenitrogenation, hydrodearomatization, or during a hydrocracking process.