FR2964326A1 - Device for dispensing polyphase mixture constituted of gaseous phase and liquid phase in reactor for hydrotreatment, hydrogenations or oxidations, comprises tray located above bed of solid particles, mixing channels, and dispersing system - Google Patents

Abstract

The device for dispensing a polyphase mixture constituted of gaseous phase and liquid phase in a reactor, comprises a tray (1) located above a bed of solid particles, mixing channels (2) such as chimneys and steam lifts equipped with bell for liquid and gaseous phases, and a dispersing system (3) of tap swirl tray that has a controlled porosity, is equipped on a part of its edge perimeter and is placed below the mixing channels and above the bed of solid particles. The mixture flows downwards through the bed of solid particles. The device for dispensing a polyphase mixture constituted of gaseous phase and liquid phase in a reactor, comprises a tray (1) located above a bed of solid particles, mixing channels (2) such as chimneys and steam lifts equipped with bell for liquid and gaseous phases, and a dispersing system (3) of tap swirl tray that has a controlled porosity, is equipped on a part of its edge perimeter and is placed below the mixing channels and above the bed of solid particles. The mixture flows downwards through the bed of solid particles. The dispersing system comprises porous or punctured separating elements (32) positioned directly under the mixing channels, holes (34, 35) with edges, and holes without edges. The holes with edges have a height of 0.1-20 mm, a diameter of 2-20 mm, and a cover. The set of holes is laid in staggered rows and arranged in square or triangular form. A distribution of holes varies according to their position with respect to center of the reactor. The separating elements: are formed by a plate positioned perpendicular to the tap swirl tray; have a height of 20-100% of the edge of the tray; and are configured for separating the mixing channels by a rectangular parallelepiped plane.

Description

The present invention relates to the field of the distribution of multiphase fluids in catalytic reactors and more particularly to a device making it possible to optimize the distribution of fluids in downwash type fixed bed catalytic reactors in hydrotreatment type applications. of diesel fuel and all hydrogenation operations operating in flowing gas-liquid flow. The present invention applies in particular in the field of gas / liquid distributors such as those used for the implementation of hydrocracking, hydrotreatment, hydrodesulphurization, hydrodemetallation, hydrodenitrogenation, selective or total hydrogenations, selective hydrogenation of steam cracking gasolines, hydrogenation of aromatic compounds in aliphatic and / or naphthenic cuts, hydrogenation of olefins in aromatic cuts. It also finds its application to implement other reactions requiring a good mixture of a gaseous phase and a liquid phase, for example partial or total oxidation reactions, amination reactions, acetyloxidation, ammoxidation and halogenation especially chlorination. The dispensing device is therefore generally disposed in an enclosure or reactor comprising an inlet of a liquid fluid and an inlet of a gaseous fluid, and containing at least one bed, for example granular solids. This device can be arranged: - either at the top of the enclosure above the bed, - or at the exit of a bed with a supply on the entire section of the enclosure on the next bed. To improve the distribution of fluids with these devices, one of the possibilities used in the prior art is for example to use dispensing trays comprising a plurality of mixing channels dedicated to the passage of gas and liquid. These mixing channels can be of different types and positioned according to different configurations on the board. Such devices are described in patent applications FR 2 807 676, FR 2 745 202, FR 2 853 260 or US 2007/0241467. The disadvantage of this type of mixing channel comes from the fact that the flow at the outlet of the mixing channel forms a relatively concentrated two-phase jet, which is problematic because the liquid does not water the entire section of the column. To overcome this problem, the pitch between the mixing channels is relatively small (between 80 and 200 mm in general) which significantly increases the amount of mixing channels and therefore increases the overall cost of the distributor plate. Another solution to improve the watering of the bed is to position under the mixing channels jet dispersion elements. There are several types of usable dispersion elements. Inserts of type elements are often attached to each mixing channel so as to disperse the jet at a wider angle, and homogeneously under the mixing channel as described in patent applications EP 2,075,056 and US 2010/0019061.

This type of solution is effective but it requires that a certain height is respected between the mixing channel and the top of the particle bed so that the jet can water widely the bed. Ideally this height should allow jets formed by neighboring mixing channels to meet. In addition, this solution is quite expensive because of the large number of dispersion elements to be manufactured.

An alternative solution, described in patent FR 2 807 673, consists in positioning jet-type dispersing elements under the plate, common to several mixing channels (or common to an entire row). Classically grids or perforated plates are used. It is important that the various elements used do not cover the entire section of the column, so that the gas can flow freely between the dispersion elements, without being forced to cross the elements themselves. The gas-liquid jet impacts the grid and disperses on its surface before raining on the bed of particles. Patent FR 2 832 075 describes an improvement of this device which consists in adding edges only on the perimeter of the grids. These flanges allow the liquid to stay at the grid and not to spill at the sides. This type of device has many advantages: it is less expensive than the inserts, allowing more to increase the pitch between the mixing channels; - The flow is distributed over the column section so it does not require a distance of jet formation under the grids. The disadvantage of this type of device is that it is limited to a certain operating range. Indeed, the geometry of the grid is optimal in a certain operating range, ie for gas and liquid velocities such that: the two-phase jets coming out of the chimneys are sufficiently broken by the grid, so distributed over a certain surface below the chimney, the retention of liquid is not too high on the grid, so that the liquid does not overflow on the sides of the grid, and that this liquid level does not pose too many problems in case of gap from plateau to flatness. This tends to limit the optimal operating range of the grids. In general, it is recommended to always operate below the liquid flow of clogging of the grids, that is to say to use a grid on which the liquid charge can not exceed a certain critical height (between 0.1 and 1 mm), and therefore use relatively open grids (opening percentage between 5 and 20%). In return, when a small flow of liquid is applied in the reactors, the grids do not break well the two-phase jet, and the distribution of the fluids is not optimal. This is particularly true in operations where the reactor is not used with its maximum capacity (turndown according to the English terminology).

This then results in a poor distribution of the liquid in the bed and a decrease in the reaction performance (loss of conversion and / or selectivity). This type of problem is encountered with chimney-type mixer channels, but can also be encountered with mixer channels of vapor lift type (also called vapor-lift according to the English terminology) or bell-type channels (also called bubble cap according to the Anglo-Saxon terminology).

It is therefore an object of the present invention to overcome one or more of the disadvantages of the prior art by providing a dispensing device, comprising a jet baffle plate whose operating range is improved thus making it possible to optimize the distribution of the flow. liquid regardless of fluid velocity. For this purpose, the present invention proposes a device for dispensing a multiphase mixture consisting of at least one gaseous phase and at least one liquid phase, said mixture being in downward flow through at least one bed of particle solids, and said device comprising at least one at least one tray above a bed of particle solids, a plurality of mixing channels of the liquid and gaseous phases, a dispersive system of pierced jet-breaker type provided on at least part of its perimeter of flanges, disposed below the mixing channels and above the bed of particle solids, said dispensing device being characterized in that the dispersive system comprises at least two types of holes. According to one embodiment of the invention, the dispersive system comprises at least one hole with flange and at least one hole without flange. According to one embodiment of the invention, the flanged hole has a height of between 0.1 and 5 mm and a diameter of between 2 and 20 mm.

According to one embodiment of the invention, the flangeless hole has a diameter of between 2 and 20 mm. According to one embodiment of the invention, the flanged hole comprises a cover. According to one embodiment of the invention, the dispersive system comprises at least one row of holes without flanges alternating with at least one row of flanged holes. According to one embodiment of the invention, the dispersive system comprises at least one row of holes comprising at least one hole without flange alternating with at least one hole with flange.

According to one embodiment of the invention, the set of holes is arranged staggered or in a square or in a triangle, with in each case a spacing pitch regular or different. According to one embodiment of the invention, the distribution of the holes is different according to their position relative to the center of the reactor. According to one embodiment of the invention, the dispersive system comprises at least one separating element formed by a solid or perforated or porous plate, having the shape of a plane rectangular parallelepiped, positioned perpendicular to the jet-breaking plate.

According to one embodiment of the invention, the separating element has a height of between 20 and 100% of that of the rim of the baffle plate and closes between 40 and 100% of the transverse section of the baffle plate. According to one embodiment of the invention, the separating element is positioned under a mixing channel or offset with respect to this mixing channel so as to be positioned between two mixing channels. According to one embodiment of the invention, the mixing channels are chimneys or steam lifts or bell-shaped channels. The invention also relates to the use of the device as described above in a reactor suitable for hydrotreating or hydrogenation or oxidation.

Other features and advantages of the invention will be better understood and will appear more clearly on reading the description given hereinafter with reference to the appended figures given by way of example: FIG. 1 is a representation schematic side view of the dispensing device according to the invention, Figure 2 is a schematic perspective view of the dispensing device according to the invention, Figure 3 is a schematic perspective view of a variant of the device of 4 is a schematic perspective view of another variant of the dispensing device according to the invention; FIG. 5 is a schematic perspective view of another variant of the dispensing device; FIG. 6 is a schematic representation seen from above of a variant of the dispensing device according to the invention. FIG. 7 is a schematic side view of an example of use of the dispensing device according to the invention.

As illustrated in Figures 1 and 2, the device according to the present invention may comprise a plurality of mixing channels such as chimneys (2) having at least one upper passage section (22) for example a bevel at its upper part and a lower passage section (23). These mixing channels may comprise a plurality of holes (21) allowing the passage of the liquid. Below the plate (1) a dispersive system type jetbreaker (3) receives the multiphase mixture formed in the mixing channels (2). The height of the mixing channels is most often between 100 and 500 millimeters (mm), preferably between 200 and 400 mm. According to one embodiment of the invention, the mixing channels can also be steam lifts. The device of vapor lift type (better known by the name of vapor-lift according to the English terminology and described in US Pat. Nos. 7,600,742 and 5,942,162) consists of tubes forming a fluid circulation circuit. M. The term elevator is explained by the fact that at first the vapor rises in the device by external tubes and in a second time the vapor descends through the central tube. According to another embodiment of the invention, the mixing channels can also be bell-shaped channels (also called bubble cap according to the English terminology). The tubes of the mixing channels protrude from the plate (1) by a height which usually varies between 10 and 200 mm and often between 25 and 50 mm. Most often the mixing channel is extended below the distributor plate to a length less than or equal to the distance between the outlet (23) of a mixing channel and the jet-breaker type plate (3). The portion of the mixing channels (2) disposed above the plate is pierced with holes (21) or slots on its periphery on one or more levels, preferably at least three levels. The means for ensuring the dispersion of the biphasic or multiphase mixture formed in the mixing channel is a dispersive system of the jetbreak type (3) located below and in the vicinity of the passage section (23) of the mixing channels. This dispersive jetbreaker system is in the form of a jetbreaker tray and can be either holed or porous. The distance between the outlet (23) of the mixing channel and the jet-off plate (3) varies most often from 5 to 500 mm, often from 10 to 200 mm and preferably from 50 to 100 mm. The jet breaker plate is often made of several separate elements and arranged at different heights (relative to the outlet (23) of the mixing channels) but all of the surfaces covers the section of the reactor. This difference in distance between the different elements of the jet-rejecting plate and the outlet (23) of the mixing channels makes it possible to leave a free passage section for the passage of the gas. The baffle plate (3) is located at a distance from the bed of granular solids selected to retain the mixture formed within said mixing channels and out of said mixing channels by said lower passage sections, to its distribution in the bed of granular solids. This distance is usually between 0 and 500 mm, and preferably between 1 and 100 mm. The jetbreak tray may be suspended from the tray (1) or the lower end of the mixer channels (2).

The jetbreaker tray (3) also has a rim (36) for containing the liquid. This flange (36) is disposed on the entire jet-breaking plate (3), these flanges possibly being themselves porous. The flanges (36) may have heights of between 0.2 and 1 times the diameter of the channels and for example between 2 and 50 mm. They can themselves have a porosity of between 0 and 80%. They can be inclined or not with respect to the vertical, and their inclination is generally between -40 ° and + 60 ° and preferably between -30 ° and + 45 °, these angle values being marked with respect to the vertical, the positive values corresponding to outwardly inclined edges of the dispersive system, and the negative values corresponding to inwardly falling edges of the dispersive system. Of course, when dispersive systems belonging to different horizontal planes are provided with flanges, the distance separating these horizontal planes must be greater than the height of the flanges. The flanges (36) may relate to only a portion of the dispersive systems, the other portion having no such flanges. It is often preferable to equip the dispersive systems located on the nearest planes of the granular solid bed with flanges.

In some cases, it may even be advantageous for a given dispersive system to have flanges on only part of its perimeter. The precise geometric shape of these flanges may vary, particularly the upper end of the flanges may be curved. In the vicinity of the rim of a dispersive system, the porosity of the dispersive system may be zero or the same as the rest of the surface of the dispersive system (3). The vicinity of the rim of a dispersive system, the area located at a distance less than or equal to 30 mm of the rim and preferably less than or equal to 20 mm of the rim. One of the functions of these flanges and their neighborhood with zero porosity, is to carry out a retaining with respect to certain impurities possibly contained in the liquid charge, particularly when it is made up of heavy hydrocarbons such as point cuts. boiling point greater than 350 ° C, as is the case in the hydrotreating units of heavy cuts diesel type. In this case, the zone of vicinity of the flanges is progressively loaded with impurities, thus avoiding the contamination of the bed of granular solids.

The jetbreak type tray according to the invention comprises at least two types of holes or perforations: holes without rim (35), at the gate, holes with flanges (34), or elevated holes which form an elevation relative to the level of the grid and which let flow only when the liquid guard (that is to say the level of the liquid on the baffle plate (3)) exceeds a certain height. The flangeless holes (35) (illustrated in Figures 1 and 2) may have a diameter of between 2 and 20 mm and preferably between 2 and 15 mm. The same tray may have flangeless holes (35) having different diameters. The holes with flanges (34) or chimneys (illustrated in Figures 1 to 5), having the shape of a tube, may have a diameter of between 2 and 20 mm, and preferably between 2 and 15 mm. The same plate may comprise holes with flanges (34) having different diameters. The height of the flange (340) of the flanged holes (34) is between 0.1 mm and 20 mm, preferably between 0.5 mm and 10 mm. In general, the height of the rims of the holes is less than the height of the edge of the plate and preferably between 5% and 50% of the height of the plate. These flanged holes (34) may comprise a cover (341, 342) or cover 15 as illustrated in FIGS. 4 and 5. The cover (341) may be partially and directly fixed to the flange (340) of the hole (34) ( Figure 4). In this way the hole remains partly open. The cover (342) can be secured with at least two tabs (343) allowing the cover to remain at a distance above the rim (Figure 5). In this way the hole remains fully open but protected by the lid (342). The arrangement on the plate, holes with rim (34) of the same height or different height, the same diameter or different diameter and holes without rim (35) of the same diameter or different diameter, can be made of all the possible ways and for example of one of the following ways but not limiting: 25 - at least one row of flangeless holes (35) alternated with at least one row of flanged holes (34), each row of holes may comprise a flangeless hole (35) alternating with a flanged hole (34), all the holes (with and without flange) may be staggered or in any other way and for example square or triangular, with in each case a regular spacing pitch or with a different spacing pitch, a larger amount of flangeless holes (35) than flanged holes (34), and for example each row may have only a few holes with flange (35), the distribution of the With rim (35) may be different depending on their position relative to the center of the reactor to take into account a possible arrow tray, 10 - a series of holes with flange (34) of different height can be alternated with holes without flange (35), - flangeless holes (35) of different diameter with flange holes (34) of different diameter and height, larger amount of flanged holes (34) than flangeless holes (35); ), and for example each row may comprise only a few holes without flange (35). The choice of number of holes with (34) or without flange (35), and their diameter, is made in such a way as to maintain an opening percentage of the jet-blower plate (3) generally comprised between 5 and 25%, and preferably between 5 and 20%. A preferred embodiment of the invention is the use of flangeless holes (35) of the same diameter, likewise no perforation, with holes with flange (34) of a few millimeters (0.5 - 3 mm) , with cover (341, 342). Indeed, for low flow rates it is important to maintain a high hole density to properly distribute the liquid using for this small sizes of holes. For higher flow rates, it is especially important to distribute the excess liquid flow over the entire reactor section, but the injection point density is less critical and the pitch may be a little higher. The cover is necessary in order to prevent liquid from passing through these holes in the absence of liquid level on the jet-breaker plate: it will make it possible to distribute the flow coming out of the chimney over a larger area of grating for the weak ones. liquid space velocities.

Since the jet-breaking plate according to the invention is intended to operate with a liquid level, the distribution will be sensitive to the lack of horizontality of the jet-breaking plate and it is therefore important to provide for the insertion of perpendicular separating plates. to the jetbreaker plate to limit the imbalances of the liquid flow on the jetbreaker plate in the event of a horizontal defect and to prevent the liquid from accumulating by gravity on the same place of the jetbreaker and then being discharged irregularly on the bed of particles. According to one embodiment of the invention (illustrated in FIG. 6), the jet-breaker plate (3) may thus comprise at least one separation element (32), also called a chicane. The baffle plate may comprise one or more separating elements (32). These separating elements may be formed by plates positioned perpendicularly to the jetbreaker plate. They generally have a height of between 20 and 100% of that of the flange (36) of the jetbreaker plate (3), and preferably between 50 and 90%. They are generally arranged in the transverse plane of the jetbreaker plate (3). According to one embodiment of the invention, the separation elements (32) are oriented in the plane perpendicular to the longest edge of the plate (3). These separating elements (32) can be arranged in different ways. They can be positioned directly under a mixing channel (2) so as to disperse its flow. They can be positioned under the mixing channels but offset with respect to the mixing channels so as to be positioned between two mixing channels. In some cases, the mechanical deflection of the jet-trays (3) is not homogeneous on the column or reactor section. This deflection strongly deforms the plate near the edge, and less strongly in the center, it is then possible to distribute the dispersion elements according to their position with respect to the flange (36) of the plate (3). The distribution of the separating elements (32) thus varies according to their position on the jetbreaker plate (3). For example, the separating elements (32) can be arranged arithmetically. In this case, the separating elements (32) are arranged between the mixing channels (2) not in a regular manner, but so as to separate a different number of mixing channels (2) and for example every 1, 2, 3 , 4 etc. mixing channels (2). They may also be arranged in greater numbers at the ends of the jetbreaker plate (3), and for example, in these areas, all the mixing channels (2) and in the middle every 2, 3, 4 etc. mixing channels (2). These examples are in no way limiting and all the positions of the separating elements (32) can be envisaged. For example, the separating elements (32) can be arranged every 1 to 10 mixing channels, and preferably every 1 to 5 mixing channels. These separating elements (32) may be in the form of a flat rectangle or any other form adapted to the jet-plate (3) used. The separating members (32) may be solid, pierced or porous so as to partially or completely close the cross-section of the jet breaker plate (3). Whatever their shape, the separating elements close between 40% and 100% of the transverse section of the plate, and preferably between 50% and 100%.

The separating members (32) are attached to the breaker plate and flange (36) by conventional fastening means. The securing system of the separating elements (23) on the jet breaker plate (3) can also be designed to close off part of the jet-breaker plate (3). The fastening system may for example comprise fastening means comprising means for closing off this type of plate which will plug one or more holes (35) without rim of the jet breaker plate (3). The plate can be round, oval, square, rectangle or other shapes. The shape and size of the plate being chosen according to the number of holes or the surface of the jet-trays (3) to be obstructed. Such a plate may for example obstruct from one to several holes. The plate may be welded or fixed with a fastening system of the screw and nut type or any other fastening system adapted to the device according to the invention. Figure 7 illustrates a simplified mode of use of the dispensing device according to the invention. The description given below as an example of application relates to a distribution system used in a reactor operating in descending mode suitable for hydrotreatments.

The reactor comprises an enclosure (5) comprising in its upper part or reactor head, a predispenser (7). The mixture dispensed by the device (7) flows downwardly to the dispenser tray (1) which is located above a first bed of granular solids (61) or catalytic bed. The plate comprises a plurality of mixing channels (2) opening on the dispersive plate type jetbreaker (3). The biphasic mixture after passing through the granular solids bed (61) is redistributed directly to a second granular solids bed (62) after passing through a second device according to the present invention.

The following examples illustrate the present invention. Examples

The following examples illustrate the present invention. Calculations show the evolution of the liquid level on the jetbreaker as a function of the liquid surface velocity (vs,). For a good operation of the aerator, it is recommended to use a grid on which the liquid height can not exceed a certain critical height (between 0.1 and 1 mm). In this height range, the jetbreaker can be considered all the more flexible as it corresponds to a wide range of vs'. All calculations are carried out with a superficial gas velocity of 10 cm.sup.-1 and a pressure of 10 MPa.Example 1 (Comparative Use of a jet-type tray (3) with flangeless holes (35). The holes are 8 mm in diameter for a triangular pitch of 36 mm.

Example 2 (Comparative) Use of a jetbreak type tray (3) with holes without flange (35). The holes are 8 mm in diameter for a triangular pitch of 22.5 mm.

Example 3 (According to the Invention) Use of a jetbreak type tray (3) with holes without flange (35) and with flanged holes (34). The holes are 9 mm in diameter for a triangular pitch of 25 mm. The flanged holes are 0.5 mm high. The arrangement of the holes on the tray is that of rows of flangeless holes (35) alternating with a flanged hole (34) (50% of each). Conclusion: The results for each of the examples are represented on the following graph 1 which represents the height of the liquid level (H liquid level in mm) as a function of the liquid space velocity (Vs, in cm.s-1). For the recommended range of liquid height on the grid (between 0.1 and 1 mm), the operating ranges are as follows for the various jet-type trays (3): example 1: between 0.15 and 0, Example 2: between 0.4 and 1.3 cm -1; Example 3: between 0.2 and 1.2 cm.sup.-1. The operating range of the jetbreaker with two types of holes is therefore wider, the grid operating with a wider range of flow rates. EXAMPLE 1 Example 2 Example 3 0 0 0.5 1 1.5 2 Vs, (cm.s-1) Chart 1: height of the liquid level (H liquid level in mm) as a function of the liquid space velocity (Vs, in The present invention should not be limited to the details given above and allows embodiments in many other specific forms without departing from the scope of the invention. Therefore, the present embodiments should be considered by way of illustration, and may be modified without departing from the scope defined by the claims.

Claims (14)

REVENDICATIONS1. Apparatus for dispensing a multiphase mixture of at least one gaseous phase and at least one liquid phase, said mixture being in downward flow through at least one bed of particle solids, and said device having at least one tray (1) located above a bed of solids of particles, a plurality of mixing channels (2) of the liquid and gaseous phases, a dispersive system of perforated jet-plate type (3), provided on at least part of its perimeter of flanges (36) disposed below the mixing channels (2) and above the bed of particle solids, said dispensing device being characterized in that the dispersive system (3) comprises at least two types of holes (34, 35). 2. Device according to claim 1, wherein the dispersive system (3) comprises at least one hole with flange (34) and at least one hole without flange (35). 3. Device according to claim 2, wherein the hole with flange (34) has a height of between 0.1 and 20 mm and a diameter of between 2 and 20 mm. 4. Device according to one of claims 2 to 3, wherein the flangeless hole 20 (35) has a diameter of between 2 and 20 mm. 5. Device according to one of claims 2 to 4, wherein the flanged hole (34) comprises a cover (341, 342). 25 6. Device according to one of claims 2 to 5, wherein the dispersive system (3) comprises at least one row of flangeless holes (35) alternating with at least one row of holes with flange (34). 7. Device according to one of claims 2 to 5, wherein the dispersive system 30 (3) comprises at least one row of holes having at least one flangeless hole (35) alternating with at least one hole with flange (34). 8. Device according to one of claims 2 to 7, wherein the set of holes is arranged staggered or in a square or triangle, with in each case a spacing pitch regular or different. 9. Device according to one of claims 2 to 8, wherein the distribution of the holes is different according to their position relative to the center of the reactor. 10. Device according to one of claims 2 to 9, wherein the dispersive system (3) comprises at least one separating element (32) formed by a solid plate or perforated or porous, having the shape of a plane rectangular parallelepiped, positioned perpendicular to the jetbreaker plate (3). 11. Device according to claim 10 wherein the separating element (32) has a height of between 20 and 100% of that of the rim (36) of the baffle plate (3) and closes between 40 and 100% of the transverse section of the jetbreaker plate (3). 12. Device according to one of claims 10 to 11 characterized in that the separating element (32) is positioned under a mixing channel (2) or offset relative to the mixing channel (2) so as to be positioned between two mixing channels (2). 13. Device according to one of claims 1 to 12 characterized in that the mixing channels are chimneys vapor lifts or channels with bell. 14. Use of the device according to one of claims 1 to 13 in a reactor suitable for hydrotreatments or hydrogenations or oxidation.