OA16611A - Filtering distribution plate intended for supplying a fixed bed reactor with downward cocurrent of gas and liquid for the treatment of heavy clogging loads. - Google Patents

Abstract

The present invention describes a distributor plate suitable for downward co-current flows of gas and liquid, more particularly in the so-called "trickling" regime, this distributor plate integrating a filtration function separate from the distribution function.

Description

The present invention is situated in the context of the filtration and distribution trays of gas and liquid at the inlet of catalytic reactors of the fixed bed type, operating in trickling flow (downward co-current, liquid velocity included below 1.5 cm. / s).

The application mainly targeted is the hydrotreatment of residues, even if the present invention can be applied to any hydrogenation of petroleum fractions which can cause clogging of the fixed bed, and more generally still, to any liquid phase, with or without gas, loaded with clogging particles, arriving on a fixed bed,

EXAMINATION OF PRIOR ART

The present invention can be seen as an improvement of several patents filed by the applicant.

- Patent FR2924950 describes a so-called predistribution filter plate with discharge tube for a fixed bed reactor with downward cocurrent of gas and liquid, this predistribution plate consisting of a filter plate placed above a conventional distributor plate.

Patent FR2889973 describes a filtering plate for a fixed bed reactor with downward cocurrent 20 of liquid gas, this plate ensuring both the functions of filtration with respect to the catalytic bed placed downstream and of distribution of the gas and liquid fluids.

This patent proposes a filter plate configuration, in which the chimneys have perforated holes (or slits) in the middle of the catalytic bed, which can pose difficulties in the case of a clogging of the bed near the holes. This clogging of the bed 25 would consequently lead to the clogging of the chimney with two consequences: an imbalance of the distribution of the liquid flow under the distributor plate, and a risk of damage to the chimneys during the dismantling of the plate with stuck chimneys and aggregated in the catalytic bed.

- Patent FR2959677 describes a set of removable baskets containing filtration particles and catalyst particles, these baskets being placed on the distributor plate in order to facilitate the assembly / disassembly of said plate and to limit the risk of aggregation between the plate and the catalyst. This solution nevertheless has a certain number '* to%

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The present invention provides substantial improvements over previous patents.

SUMMARY DESCRIPTION OF FIGURES

FIG. 1 is a side view of the plate according to the invention in which the main elements are recognized; filtration layer (4) supported by a perforated support (3), distribution elements (5) supported by the solid plate (2), porous lower grid (7).

BRIEF DESCRIPTION OF THE INVENTION

The present invention can be defined as a distribution plate intended for supplying a catalytic reactor operating on a gas and liquid feed, more particularly in a flow regime called a trickling regime, that is to say with a surface speed liquid between 0.1 cm / s and 1.5 cm / s.

The present plate can be defined as a distributor plate whose function is to transform the two-phase jet entering the reactor into a liquid gas mixture uniformly distributed over the surface of the catalytic bed placed downstream of said plate. The distributor plate according to the invention also integrates a filtration function incorporated within the plate itself by the installation of a filtration layer. This filtration layer, unlike the trays according to the prior art, is to some extent separate from the distribution function, since the distribution elements do pass through the filtration layer, but the gas and liquid inlets to the inside the distribution elements are located outside of said filtration layer.

Generally these distribution elements have the form of substantially vertical chimneys extending from a lower level located below the level of the tray, to an upper level located above the upper surface of the filtration layer.

The gas is admitted through the open upper end of the distribution elements, said upper end being located above the filtration layer, and the inlet of the

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liquid is made through a row of orifices, this row being located in the part located below the filtration layer (4) and above the plate (2) itself.

This part is occupied only by the liquid, since in normal operation, the liquid level above the plate (2) is located inside the filtration layer (4) and below the upper end of the distribution elements (5) which are only accessible to gas.

The distribution and filtration plate according to the present invention is therefore suitable for a downward cocurrent liquid gas flow, in a fixed bed reactor which may include several catalyst beds staged along the reactor.

In general, the filter plate according to the invention is positioned upstream of the first catalytic bed (in the direction of the flow of fluids). When the feed is introduced in a staged manner onto different catalytic beds staggered along the reactor, it is possible to position a filter plate according to the invention upstream of each of the catalytic beds. The invention can therefore be defined as a fixed-bed reactor with a descending co-current liquid gas flow comprising a distribution and filtration plate adapted to said flow, said fixed-bed reactor possibly comprising several catalyst beds staged along the reactor, each distribution and filtration plate being positioned upstream of each catalytic bed, said plate being made up from top to bottom of the following elements:

- a perforated support (3) not covering the entire section of the reactor, but leaving free an annular zone (11) corresponding to 5% to 50% and preferably 5% to 30% of the section of said reactor,

- a filtration layer (4) supported by the perforated support (3),

- a solid plate (2) located at a distance between 50 mm and 150 mm relative to the perforated support (3), comprising a plurality of substantially vertical distribution elements (5) passing through the filtration layer (4) and the full plate (2), these distribution elements (5) being arranged in a rectangular or triangular pitch, said distribution elements (5) having a height of between 200 mm and 400 mm, being open at their upper end for admission gas and comprising at least one row of holes located in the portion of said distribution elements which is between the perforated support (3) and the full plate (2), for the admission of the liquid, and the liquid gas mixture being discharged through the lower end of said distribution element,

- at least one dispersive element (7) of high porosity located below the solid plate (2) at a distance between 20 mm and 300 mm, and preferably between 50 mm and 150 mm relative to the latter.

The term full plate (2) means that this plate does not have an orifice, the exit of gas and liquid being via the lower ends of the distribution elements (5).

According to one variant, the dispersive elements (7) which have as their objective the dispersion of the liquid jet below each distribution element (5), are of the deflector type.

They can also consist of porous grid elements arranged in staggered rows under the solid plate (2) at distances which range between at a distance between mm and 300 mm, and preferably between 50 mm and 150 mm per compared to the latter.

Preferably in the distribution and filtration plate according to the present invention, the distribution elements (5) consist of substantially vertical chimneys with a total height of between 200 mm and 400 mm.

Preferably, in the distribution and filtration plate according to the present invention, the filtration medium (4) deposited on the perforated support (3) consists of at least one layer of so-called protective particles, with a height of between 100 mm and 300 mm, and preferably less than 150 mm.

The particles constituting the filter medium (4) can be:

either particles of guard material or any other particles generally serving as protective elements, or particles of the catalyst itself.

The present plate is not linked to the choice of the guard material constituting the filtration layer. Any material capable of retaining the clogging particles contained in the filler may be suitable for the plate according to the present invention.

For heights of the filtration medium of between 200mm and 300mm, several layers can be used, the first consisting of particles of guard material, and the following of particles of catalyst. In most cases, a single coat is sufficient.

Preferably, in the distribution and filtration plate according to the present invention, the dispersive elements (7) of high porosity located below the solid plate (2) are ftL · · ·

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made up of pieces of grid arranged in staggered rows, and alternating between a distance of 150 mm and a distance of 250 mm below said plate (2).

Preferably, in the distribution and filtration plate according to the present invention, a protective grid or perforated plate (6) intended to break up the liquid jet entering the reactor above the filtration layer (4) is arranged above said filtration layer, at a distance from said layer of less than 10 mm.

According to one variant, the grid (7) can be replaced by any deflector-type element which aims to disperse the liquid jet below each distribution element (5), each deflector being placed under each, or under only a part. , distribution elements (5).

In general, the distribution plate according to the present invention can be used in any process making use of a downward co-current flow of gas and liquid in the so-called trickling regime, that is to say with a surface speed of the liquid included between 0.1 and 1.5 cm / s.

More particularly, the distribution plate according to the present invention applies to the processes of hydrotreatment, selective hydrogenation, conversion of residues, or oxidation of petroleum fractions with a number of carbon atoms ranging from 3 to 50, preferably. ranging from 5 to 30.

The heavy loads likely to be treated by means of this filtering distributor plate can be defined as those whose boiling point is greater than 370 ° C, in particular of the residue or related type: atmospheric residues, vacuum residues, deasphalted oils, or else residues resulting from conversion processes such as, for example, coking, hydrotreatment in a fixed bed, in an ebullating bed, or in a moving bed, all these types of residues possibly being taken alone or as a mixture.

These heavy loads can be used as such or diluted with a hydrocarbon fraction or a mixture of hydrocarbon fractions.

The heavy loads concerned by the present invention can also comprise cuts resulting from the process for liquefying coal, aromatic extracts, or any other hydrocarbon cuts.

DETAILED DESCRIPTION OF THE INVENTION

The distributor plate according to the present invention is a distributor plate in the sense that it transforms the two-phase jet (liquid gas) entering the reactor into a homogeneous liquid gas mixture which is uniformly distributed over the surface of the catalytic bed located downstream.

It also incorporates a filtration function, but unlike the filter plates of the prior art, the filtration function is separate from the distribution function.

The perforated support (3) on which the filtration layer (4) is deposited is located in a central zone of the plate, but does not occupy the entire section of the reactor. There is in fact an annular space (11) between the filtration zone (4) and the walls of the reactor (1).

This annular space (11) allows the passage of the liquid towards the distribution elements (5) in the situation where the filtration layer (4) is blocked by the various impurities recovered over time.

The width of this annular space is established so that the pressure balance is respected even in the case where the plate is completely clogged.

In this case, the filtration function is no longer ensured, the distribution plate continues to operate because the liquid inlet holes (10) inside the distribution elements (5) are located in an area completely clear of the filtration layer (4).

This free area of the filtration layer has a height of less than 300 mm, preferably less than 200 mm and, for the distribution to function correctly, the height of the distribution elements (5) must be greater than 200 mm, preferably greater than 300 mm, because this height makes it possible to absorb the variation in liquid flow rate often required by the process.

The filtration zone (4) uses a perforated support (3) connected to the distributor plate (2) and mechanically held to this plate (2) by any means known to those skilled in the art, such as for example an elbow support (9) as shown in Figure 1, and / or a vertical support (as also shown in the center of Figure 1), or any other means known to those skilled in the art.

The plate (2) and the perforated support (3) can be held together by a screw system or by any other means known to those skilled in the art.

The perforated support (3) can be perforated in its lower zone but also in its lateral part to allow the passage of the liquid.

The distribution elements (5) generally have the form of substantially vertical chimneys extending from a lower level located below the plane of the plate (2) to an upper level located above the upper surface of the filtration layer. (4). These distribution elements (5) can be protected by non-perforated sleeves (8). Therefore, the filter bed (4) has no contact with the distribution elements (5).

If the filtration bed solidifies, it clings to the sleeves, but not to the distribution elements (5) themselves. Thus the lower plate (2) is not damaged, and the separation of the clogged filtration zone (4) from the rest of the plate is made much easier.

For assembly and disassembly, the perforated support (3) is fed by plates onto the distributor plate, these plates being of such size that they can be introduced through the manhole of the reactor. Likewise, the distributor plate (2) is cut into elements which can be introduced through the manhole.

The sleeves (8) can be placed directly on the perforated support (3), around the distribution elements (5) of the distributor plate.

The filtration medium (4) is deposited directly, by a bulk load, on the perforated support (3).

Optionally, a protective grid (6) can be added above the filter medium (4) to protect said medium from the arrival of the gas / liquid flow entering the reactor, in order to avoid any projection of the particles constituting said layer of filtration.

The advantages of the distribution plate according to the present invention over the plates of the prior art can be summarized as follows:

the liquid inlet holes of the distribution elements (5) are located below the perforated support (3), and this arrangement makes it possible to separate the filtration function and the distribution function, this distribution also ensures a certain flexibility on the liquid flow, because the liquid level can be established over a fairly wide range of heights going from a lower level located in the filtration zone (4) to an upper level located above the filtration layer (4), but which must however remain below the upper end of the distribution elements (5) to avoid the intrusion of liquid by said upper ends which serve for the passage of gas.

the filtration height remains sufficient to fulfill the desired filtration function,

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- assembly and disassembly are easier compared to the previous solution of filter baskets:

o arrival of the perforated support (3) by plates through the manhole;

o perforated support (3) supported by several reinforcements / tabs towards the wall and / or the distributor plate;

o protective sleeves (8) to be slipped around the distribution elements (5), manufactured independently on the outside and placed directly on the solid support (2);

o arrival of the solid support (2) provided with distribution elements (5) by plates through the manhole;

The distribution plate according to the present invention can be fitted to new units or can replace conventional technology plates on existing units.

For certain types of plates (for example the case of EquiFlow® marketed by Axens), a remodeling of said plates is sufficient to install the filter plate described in the present invention.

EXAMPLES ACCORDING TO THE INVENTION

The present example is given purely by way of illustration and relates to a residue hydrotreatment.

The gas and liquid velocities are between [2 - 5] cm / s for gas, and [0.1 - 0.5] cm / s for liquid.

The diameter of the reactor of 3.5 m.

The dimensioning of the distribution elements which have the form of vertical chimneys (5) is as follows:

- Height of the chimneys: 350 mm

- Chimney diameter: 50 mm

- Pitch between chimneys: 200 mm

The chimneys have two rows of orifices (10) for the admission of the liquid:

- Row 1 of holes: height in relation to the full plate of 40 mm, 3 holes of 5 mm

- Row 2 of holes: height in relation to the full plate of 130 mm, 3 holes of 5 mm

- Opening for the passage of gas at the top of the chimney for gas admission: 30 mm “. t

The sizing of the filtration layer (4) is as follows:

- Position of the perforated support (3): 140 mm above the full plate (2)

- Diameter of the filtration layer (4): 3.1 m

- Thickness of the annular zone (11): 200 mm

- Total height of the perforated support (3): 160 mm, i.e. 310 mm above the full plate (2), and 10 mm below the gas opening of the distribution elements (5)

- Position of the protection plate (6): 290 mm above the full plate (2)

- Thickness of the guard material layer: 150 mm

Claims (9)

5 l) Fixed-bed reactor with downward cocurrent gas liquid flow comprising a distribution and filtration plate adapted to said flow, said fixed-bed reactor possibly comprising several catalyst beds staggered along the reactor, each distribution plate and filter being positioned upstream of each catalytic bed, said plate being made up from top to bottom of the following elements: 10 - a perforated support (3) not covering the entire section of the reactor, but leaving free an annular zone (11) corresponding to 5% to 50% and preferably 5% to 30% of the section of said reactor, - a filtration layer (4) supported by the perforated support (3), - a full platform (2) located at a distance between 50 mm and 150 mm from the 15 perforated support (3), comprising a plurality of substantially vertical distribution elements (5) passing through the filtration layer (4) and the solid plate (2), these distribution elements (5) being arranged in a rectangular pitch or triangular, said distribution elements (5) having a height of between 200 mm and 400 mm, being open at their upper end for the admission of gas and comprising at least one row of holes 20 located in the portion of said distribution elements which is between the perforated support (3) and the full plate (2), for the admission of the liquid, and the liquid gas mixture being discharged through the lower end of said element of distribution, - at least one dispersive element (7) of high porosity located below the solid plate (2) at a distance between 20 mm and 300 mm, and preferably between 50 mm and 25 150 mm from the latter. 2) Fixed bed reactor with downward current flow of gas and liquid according to claim 1, wherein each distribution and filtration plate comprises distribution elements (5) which are substantially vertical chimneys surrounded by solid sleeves. (8) on the height portion which corresponds to the crossing of the filtration layer (4). "L 3) Fixed bed reactor with downward flow co-current of gas and liquid according to claim 2, wherein the pitch of the chimneys is between 100 and 300 mm. 4) Fixed bed reactor with downward co-current flow of gas and liquid according to claim 1, wherein the filtration layer (4) supported by the perforated support (3) consists of at least one layer of particles of guard material, with a height between 10O mm and 300 mm. 5) Fixed bed reactor with downward flow co-current of gas and liquid according to claim 1, wherein the dispersive elements (7) of high porosity located below the solid plate (2) are arranged in staggered rows and alternate between a distance of 150 mm and a distance of 250 mm below said plate (2). 6) Fixed bed reactor with downward co-current flow of gas and liquid according to claim 1, wherein above the filtration layer (4) is arranged a protective grid (6) intended to break the incoming liquid jet in said reactor. 7) Fixed bed reactor with downward co-current flow of gas and liquid according to claim 1, wherein the dispersive elements (7) are constituted by a set of conical deflectors, each deflector being placed under a distribution element (5) ). 8) Use of the fixed bed reactor with downward co-current flow of gas and liquid according to claim 1, in a hydrotreatment process, selective hydrogenation, conversion of residues, or oxidation of numbered petroleum cuts. carbon atoms ranging from 3 to 50, preferably ranging from 5 to 30. 9) Use of the fixed bed reactor with downward co-current flow of gas and liquid according to claim 1, in any process using a downward co-current flow of gas and liquid in the so-called trickling regime, c ' ie with a surface velocity of the liquid of between 0.1 and 1.5 cm / s. 0 2 OCT. 2013