WO2021213747A1

WO2021213747A1 - Reactor for a catalytic process

Info

Publication number: WO2021213747A1
Application number: PCT/EP2021/057221
Authority: WO
Inventors: Lone Skikkild GAVNHOLT; Marc Nybo HAMMER; Rasmus Asker CALUNDANN; Ali SABOORI; Klaus Risbjerg Jarlkov; Mark Harrison THOMAS
Original assignee: Haldor Topsøe A/S
Priority date: 2020-04-20
Filing date: 2021-03-22
Publication date: 2021-10-28

Abstract

A reactor for a catalytic process comprising catalyst beds has catalyst bed supports with an improved sealing system and improved profile.

Description

Reactor for a catalytic process FIELD OF THE INVENTION

This invention relates to a reactor comprising catalyst supports, specifically a multi-catalyst-bed hydroprocessing reactor with a catalyst support for each catalyst bed. Specifically, the catalyst support is for use in radial flow and top- down-flow catalytic reactors which include vertically superimposed packed beds of particulate catalytic material wherein a liquid, liquid and gas mixture or vapour is processed as it flows down through the packed beds. Quench gas may enter at intermediate positions of the reactor. This type of reactor is used in the petroleum and chemical processing industries for carrying out various catalytic reactions, such as sulphur and nitrogen conversion (HDS/HDN); hydrogenation of: olefins (HYD) and aromatics (hydrodearomatisation - HDA), metals removal (hydrodemetallisation - HDM), oxygen conversion (hydrodeoxygenation - HDO) and hydrocracking (HC) and synthesis reactions.

BACKGROUND OF THE INVENTION

Hydroprocessing is taking place in a hydroprocessing catalytic reactor which is the key element of a hydroprocessing unit. Hydroprocessing catalytic reactors can have single or multiple catalyst beds. The number of catalyst beds within one reactor follows from the calculation of the maximum height of the bed, in the individual process and function. This is decided based on a number of constraints. These include catalyst activity and selectivity, catalyst lifetime, flow distribution considerations and safety.

The one or more catalyst beds in the reactor need to be supported to retain the catalyst but the support must enable process fluid to flow through the support to be processed In the reactor bed(s). Catalyst support grids in the reactor are built by a number of cassettes, each with a weight of 100-500 kg. The cassettes comprise a frame, a grid and a screen on top. As crane time often determines the time for assembly and disassembly of the catalyst support grid, the disassembly time is often in the range of 2 days, roughly the same as the assembly time. The screen covering the catalyst support is retaining the catalyst pellets. To enable through-flow of process fluid, the screen may be made of for example woven wire-mesh, flat printed pattern or welded wires and rods. Between the cassettes and the support of the cassettes as well as in-between each of the cassettes, a gasketing is necessary to prevent the catalyst from entering the void, passing to the level below the cassettes or building up of a blocking in the voids which may fix the cassettes so they cannot be disassembled and which may lead to building tensions in the structure as the reactor heats up and cool down. Installing the gasketing around the cassettes when installing them and whenever they are moved for service is with state of the art technique cumbersome, time-consuming and may present a health risk. The cassettes, more particular the frame and grid of the cassettes need to have a minimum strength to support the load of the above catalyst bed and any dynamic load during operation. This leads to a notable height of the cassette, typically between 200 and 1200 mm, a height and thereby volume which has to be taken from the active volume of the reactor.

During operation, the functionality of the screen may be affected for example by coke deposition, by damaging during handling such as scaffolding on top of the screen, and occasionally by corrosion. When damaging occurs, the support grid needs to be dismantled, the affected cassette is brought to the workshop, where it is cleaned and repaired. Dismantling and reparation is cumbersome and time consuming. Some types of screens, e.g. some welded wires and rods screens may not be able to be repaired and the whole cassette needs to be replaced by a new.

US2012237415 discloses a modular catalyst bed support can be used to increase the number of catalyst beds available in a reactor. The modular catalyst bed support can include a lattice with a plurality of lattice openings and modules inserted into the lattice openings. The modular catalyst bed support can rest on top of an underlying catalyst bed, which can reduce or eliminate the need for attachment of the modular catalyst bed support to the walls of the reactor.

US2013064731 is directed to an upwardly convex fixed-bed catalyst support for a hydroprocessing reactor. The catalyst bed support includes an upwardly convex annular-shaped plate having an outer end in communication with the reactor inner surface, and an inner end in communication with a horizontal hub assembly.

US2745722 describes a reactor comprising a wall defining a reaction chamber containing a horizontally disposed bed of finely- divided catalyst, calking apparatus for depositing a supply of fresh catalyst about the peripheral edge of said catalyst bed in order to compensate for radial contraction thereof, said calking apparatus comprising a gas-tight seal in said wall above said catalyst bed, a rotatable conduit of comparatively small cross-sectional area entering said chamber through said seal and terminating in a discharge end at a point above and in proximity to the peripheral edge of said catalyst bed, and means connected to said conduit for maintaining said discharge end of said conduit above and in close proxitnity to said peripheral edge as said conduit is rotated.

US2860860 is describing a tray deck for a gas-liquid contact column. It comprises a number of parallel spaced beams extending across the column and supported at their ends by an annular flange secured, e.g. by welding, to the shell of the column and a plurality of deck sections which extend transversely between adjacent beams and which have along their transverse edges downwardly projecting stiffening flanges extending between the beams. The deck is completed by deck sections which rest partly on a beam and partly on the flange, the edges of the sections adjacent the shell being curved. The beams are secured to the flange by clamping members secured together by a bolt which may pass through a hole in the top flange of a beam or the upper flange may be notched to accommodate the stem of the bolt. The deck sections may be made of light gauge sheet metal, e.g. of stainless steel, nickel or "Monel" metal, (R.T.M.) and are of such sizes that a space is left between adjacent sections on the beams and between the sections and the shell of the column to allow for expansion. The sections have series of punched out slots with sharp or rounded corners to provide an aggregate slot area of between 7 and 50 per cent of the total tray area. The sections have centrally disposed reinforcements secured to their undersides and the transverse marginal edges of the sections are bent downwardly to form the stiffening flanges and may also have a tip turned inwardly from a flange under a reinforcement. The longitudinal edges of the sections extend beyond the flanges. The sections are of similar construction except that they have only one transverse stiffened edge and the reinforcements stop short of the curved edges of the sections. The sections are secured to the beams by bolts and washers, the washers being of such size as to overlie the marginal portions of adjacent sections and the seams of the bolts passing between the sections which are notched for this purpose if necessary. A section is provided in each tray deck to serve as a man-way and is secured by fasteners having removable nuts at both ends of a threaded bolt to a central portion of which is secured a plate adapted to lie between adjacent longitudinal edges and prevent rotation of the fastener.

US2012156111A discloses structure and method for adding a catalyst bed platform to an existing reactor without welding to the structural portion of the reactor walls. The structure is constructed from components that can be passed through an existing opening in a reactor. The structure allows a catalyst bed in an existing reactor to be divided into catalyst beds with a reduced length to diameter ratio.

US5891405A describes an exothermic heterogeneous catalytic synthesis reactor including at least one catalytic bed arranged in a cylindrical shell and provided with a bottom plate for containment of the catalyst, and at least one supporting shoulder for the bottom plate extending from the shell, includes a catalyst-seal support device including an annular element placed between the shoulder and the bottom plate. The annular element is fixed in a removable manner with the bottom plate and has a thermal expansion coefficient substantially equal to that of the shell.

EP0602288 discloses a moving catalyst bed reactor comprising a normally vertical cylindrical vessel provided at its upper end with a catalyst inlet and a reactant inlet and at its lower end with a catalyst outlet and an effluent outlet, and with a separation device arranged in the vessel near its lower end, the separation device comprises a downwardly tapering catalyst support having an outer edge which is joined to the wall of the vessel and a central opening which communicates directly with the catalyst outlet, the catalyst support is provided with perforations and with fluid withdrawal devices having screens preventing catalyst from passing which fluid withdrawal devices are arranged over the perforations and joined to the catalyst support.

In US6878351 , a catalyst support structure e.g. for use in an ammonia oxidation reactor is disclosed, comprising a series of primary supports disposed above a catalyst bed, a lattice assembly disposed beneath the catalyst bed and on which the catalyst bed rests, said lattice assembly being suspended from the primary supports by suspending means extending through the catalyst bed. Preferably the support structure includes a static start-up burner arrangement in the form of one or more perforated tubes adjacent the primary supports.

In W09110496, A catalytic reactor for gas phase reactions is disclosed. The reactor includes a housing, a porous catalyst support plate within the housing, a bed of catalyst particles within the housing and a fibrous filter pad extending across the housing to prevent transport of catalyst particles from the housing. The filter pad is resistant to clogging and imposes a low pressure drop across the reactor. US5527512 discloses a light-weight and easily manufacturable catalyst support structure, which allows fluid flow into a catalyst bed in uniform distribution. The support structure, used for supporting a moving catalyst bed within a moving bed reactor having an upward flowing fluid phase, is formed in a cone-like shape in which the diameter enlarges upward. The supporting structure comprises a shell-like support member, a first mesh layer comprising thick mesh elements, and a second mesh layer having a mesh size which does not allow catalyst particles to pass through. The first mesh layer overlays the support member, and the second mesh layer overlays the first mesh layer. The shell-like support member includes a circular bottom plate extending perpendicular to the center line of the reactor, and a side wall having a truncated cone shape which extends upward from the edge of the bottom plate. The bottom plate and the side wall are primarily made of perforated plates through which the fluid passes. A plurality of cylindrical flow guides of different diameters are provided underneath the shell-like support member.

There is a need for a reactor with a catalyst support which can be easily and quickly serviced and replaced and with an optimized sealing solution around the catalyst support cassettes to lower the down-time of the reactor and thus lower the service costs. Further there is a need for a reactor with a catalyst support with an optimized strength / inactive volume ratio, so the output of the reactor can be optimized for a given reactor volume.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a reactor with a catalyst support comprising cassettes which has an improved sealing system for the cassettes, where the cassettes have an optimized profile to reduce the inactive volume of the reactor and where the cassettes are easily serviced since they have a screen part which can be quickly removed and replaced without disassembly of the cassettes. The reactor suited for a catalytic process according to claim 1 of the invention, is a reactor with one or more catalyst beds, each bed comprises a plurality of catalyst pellets or catalyst members of another form or type. To contain the catalyst beds, the reactor comprises a bottom support for each catalyst bed.

The support is constructed as a grid e.g. as a number of support beams and further comprising a number of cassettes, which rest on the support beams. The cassettes are sealed together to prevent by-pass of the process gas, which would result in an uneven flow of the process gas through the chemically active catalyst bed. Because of the grid structure of the cassettes, the process gas is able to pass through the cassettes, but since the catalyst pellets are normally smaller than the apertures in the cassette grid, a screen is applied on the top of the cassette grid, with apertures large enough to allow flow through of process fluid, but small enough to retain the catalyst pellets and hence together with the grid they form a bottom support for the catalyst bed. At least one of the support beams comprise support beam sealing means and a plurality of the cassettes comprises a protruding cassette sealing which co-operates with the support beam sealing means to provide a sealing between the at least one support beam and a plurality of the cassettes. The sealing provided by the co-operating support beam sealing means and the protruding cassette sealing is tight enough to prevent catalyst pellets from passing in between the support beam and the cassette and it thereby obviates the use of a gasketing as normally known in the art, providing quicker, safer and cheaper mounting and service of the cassettes.

In an embodiment of the present invention, the screen is removable fastened to the cassette. The screen may be fixed to the underlying cassette by quick release means. This enables the screen to be fixed to or detached from the cassette by hand or by hand tools in less than 30 minutes or even in less than 5 minutes for each screen. The time it takes depends of a variety of parameters e.g. the amount of free space for the personnel to operate in when they service the screen, the weight of the screen, the type of release means etc. The release means may comprise a simple screw or a nut, a hole-nut or a hole-screw, a knee-joint quick release, an eccentric quick release, a wedge type quick release just to mention a few of the many known in the art. As described, the release means may either be operable by hand or with the use of hand tools.

In an embodiment of the invention, the protruding cassette sealing may be an integrated part of the screen. In a specific embodiment, the protruding cassette sealing may simply be a prolongation of the screen itself. In the case, where the screen is removable fastened to the cassette, the sealing may have very small tolerances as it may be tightened to the support beam sealing means when the screen is fixed to the underlying cassette.

The support beam sealing means may in an embodiment be a protruding lip which is attached to the side of the support beam. This embodiment also enables the present invention to be used when retrofitting existing reactors.

In a specific embodiment of the invention, the cross-sectional area of at least a part of the cassette grid, when seen in a side view is load optimized. The load of the cassette grid resembles an evenly distributed load on a beam, and the load is thus smallest at the ends of the cassette grid beams and largest in the middle section of the cassette grid. Therefore, it is possible to reduce the grid height near the ends, the edge of the cassette without compromising the load strength of the cassette. The reduced height near the edge of the cassette can be utilized to reduce the overall height of the internals, the equipment in the reactor, which again leaves more volume in the reactor for active material, increasing the output of the reactor.

In a further embodiment of the reactor, at least one of the cassettes comprises an inspection port. As the catalyst support comprises a plurality of cassettes, the ability of providing a cassette with an inspection port provides a freedom to position one or more inspection ports where it best suits the purpose for service and maintenance. The inspection port may comprise any form as known in the art and in a specific embodiment, it may be a part of the catalyst grid which is removable; together with a removable screen, this provides a simple and easy to operate inspection port well integrated into the whole of the catalyst support grid.

In an embodiment of the invention, the apertures of the screen each has an area of between 500 mm2 and 0.1 mm2. The area of each aperture is according to claim 1 off course small enough to retain the catalyst pellets, since this is the function of the screen. But to lower the pressure loss of the process gas and to save material and production costs, the aperture size may be made as large as possible while still keeping the supporting function. Since the catalyst particles may break during operation, it may be necessary to account for smaller particles than the actual catalyst particle size when loaded into the reactor. The shape of the apertures may be any suitable shape regarding function and cost of manufacture. Examples are quadratic, rectangular or any other suitable shape. In a further embodiment of the invention, the apertures of the screen each has an area of between 100 mm2 and 1 mm2 for the same reasoning as explained above.

In further embodiments of the invention the screen is made in a range of structures. In one embodiment the screen is made by a woven wire mesh. The wire is strong enough to carry the weight of the catalyst bed as well as the pressure induced to the catalyst bed by the flow of the process gas during operation. The screen may however be supported by the underlying support grid of the cassette and in such case the dimension of the wire may be reduced. To support the wire mesh, this embodiment of the invention may further comprise an outer frame to which each end of the wires in the wire mesh is fixed. In a variety of this embodiment the mesh may instead of only wire, be a combination of wire and rods welded together. In this variety, the rods contribute to the strength of the screen to a larger amount than the wire due to the rods higher strength. In a further embodiment of the invention, the screen may comprise a flat printed pattern, e.g. in the form of a steel plate with a pattern of apertures in the plate made in any known way of the art. The apertures may thus be made by stamping or laser cutting of the steel plate.

The cassettes may each have a weight of 100-500 kg. Therefore, the crane time may determine the time for assembly and disassembly of the catalyst support grid, as explained above. This makes assembly and disassembly of the catalyst bed support slow and expensive. To solve this problem the screen applied on the top of the cassette grid is removable fastened to said cassette according to claim 1 . Hence the screen can be removed by hand power, since it is much lighter in weight than the total cassette.

In a specific embodiment of the invention, the weight of the screen is below 100 kg, which makes it removable by hand power when using hand tools and the hand power of more than one person. In a further embodiment of the invention, the screen may even be removable by the hand power of a single man as the weight of the screen in this embodiment is below 25 kg.

The screen may in a specific embodiment be rectangular and it may be fixed to its underlying cassette in each of its four corners. In a specific embodiment of the invention, the reactor comprises screens of which a majority are rectangular. When employing cassettes and screens of rectangular shape in a reactor with a circular cross section, a number of the cassettes and screens will have a shape different from rectangular such as triangular-like with two straight sides and a third side which is arc-shaped, in order to fit the entire cross- section.

In a certain embodiment of the invention, the reactor is a hydroprocessing reactor, and in a further embodiment of the invention, the reactor is used for a hydroprocessing process. FEATURES OF THE INVENTION.

1. Reactor for a catalytic process with one or more catalyst beds, comprising at least one support beam and support beam sealing means, a bottom support for each of said catalyst beds, the bottom support is constructed as a grid comprising a plurality of cassettes, each cassette is covered by a permeable screen with apertures large enough to allow flow through of process fluid, but small enough to retain the catalyst pellets, wherein a plurality of said cassettes comprises a protruding cassette sealing and said protruding cassette sealing co-operates with and seals with the support beam sealing means.

2. Reactor according to feature 1 , wherein said screen is removable fastened to said cassette.

3. Reactor according to any of the preceding features , wherein the protruding cassette sealing is an integrated part of the screen.

4. Reactor according to any of the preceding features, wherein the support beam sealing means is a protruding lip attached to the side of the support beam.

5. Reactor according to any of the preceding features, wherein the protruding cassette sealing, and the support beam sealing means create a seal tight enough to retain the catalyst pellets.

6. Reactor according to any of the preceding features, wherein the cross-sectional area of at least one of the cassettes grids is load optimized with a lower profile height in the ends of the cross sectional profile than in the middle of the cross sectional profile. 7. Reactor according to any of the preceding features, wherein at least one of said cassettes comprises inspection ports.

8. Reactor according to any of the preceding features, wherein the apertures of the screen each has an area of between 500 mm2 and 0,1 mm2.

9. Reactor according any of the features 1 - 7, wherein the apertures of the screen each has an area of between 100 mm2 and 1 mm2.

10. Reactor according to any of the preceding features, wherein the screen is made by woven wire mesh.

11. Reactor according to any of the features 1 - 9, wherein the screen is made by welded wires and rods.

12. Reactor according to any of the features 1 - 9, wherein the screen is made by a flat printed pattern.

13. Reactor according to any of the preceding features, wherein the weight of the screen is below 100 kg.

14. Reactor according to any of the features 1 - 12, wherein the weight of the screen is below 25 kg.

15. Reactor according to any of the preceding features, wherein the screen is fixed to the cassette by means of quick release means, enabling the screen to be fixed to or detached from the cassette by hand or by hand tools. Reactor according to any of the preceding features, wherein the reactor is a hydroprocessing reactor, a hydrogenation reactor, a TIGAS reactor, or a methanation reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further illustrated by the accompanying drawings showing examples of embodiments of the invention.

Fig. 1 shows a top view of parts of the catalyst support grid in the inside of the reactor according to an embodiment of the invention,

Fig. 2 shows a top view of a part of the catalyst support grid according to an embodiment of the invention,

Fig. 3 shows an isometric top/side view of a part of the catalyst support grid according to an embodiment of the invention, Fig. 4 and 6 shows a detail side view of a standard solution according to state of the art.

Fig. 5 shows a detail side view according to an embodiment of the invention. Fig. 7 shows a further detail side view according to an embodiment of the invention.

Fig. 8 shows Fig. 7 in isometric side view.

POSITION NUMBERS

01. Support beam

02. Support beam sealing means 03. Cassette.

04. Protruding cassette sealing. 05. Screen.

06. Frame.

07. Grid of cassette. 08. Support ring

09. Cassette support.

DESCRIPTION OF THE DRAWINGS

A number of embodiments of the invention will be explained in more detail in the following with reference to the drawings.

Fig. 1 shows a top view of the inside of a reactor according to the invention. Parts of a catalyst support is visible in partly assembled state to best visualize the different parts. On the inside of the reactor wall, a support ring 08 is mounted. The support ring supports two support beams 01 and a number of cassettes 03 and grids of cassettes 07. On the furthest right side of the view, three grids of cassettes without the screen mounted is shown arranged in close connection to each other. As can be seen, the outline of the cassettes is constructed to fit the inside contour of the reactor wall, as well as the side of the support beam and neighbouring cassette grids. In the middle section of the catalyst support, between the two support beams, seven cassettes are shown installed, resting on the support ring and on the support beams. These cassettes are shown with the screens 05 mounted, ready to support the catalyst bed.

A part of the catalyst support can be seen in more detail on Fig. 2. Two cassette grids are shown, the cassette grid between is not mounted. It is visible how the cassettes can rest on a protrusion on the support beam and on the support ring. Also it is visible in more detail how the cassettes comprise a supporting grid construction.

In Fig. 3 it is shown how a cassette including its outer frame 06 (but without the screen) is mounted between two neighbouring cassettes (also without the screens mounted). To stabilize and seal the gap between the cassettes, a cassette support 09 is arranged between the adjacent frames of the cassettes. This sealing material, the cassette support 09 may be omitted at least to an extent as a consequence of this invention as will be shown in the following drawings. On Fig. 4 it is shown in a detail side view how the cassette is supported on the support beam according to known state of the art, where a cassette support is arranged in the gap between the cassette outer frame and the side of the support beam. However, in Fig. 5 the same detail side view shows how the cassette support may be omitted and replaced with another type of sealing according to this invention. A support beam sealing means 02, in this embodiment in the form of a protruding lip structure is fixed to the side of the support beam is a suitable location. The support beam sealing means cooperates with a protruding cassette sealing 04, which in this embodiment is in the form of a suitable extension of the screen. The protruding cassette sealing overlaps with the support beam sealing means with tolerances narrow enough to prevent catalyst material to enter down into the gap between the cassette side and the support beam side. It is to be understood that the size of the overlap as well as the space between the underside of the protruding cassette sealing and the upper side of the support beam sealing means (if any) is specifically calculated with reference to the catalyst material size, the tolerances of the reactor interior and the cassettes, the operation temperatures and loads etc. The overlap arrangement of the co-operating support beam sealing means and the protruding cassette sealing means allows for some material movement according to varying tolerances, temperatures and loads.

Fig. 6 shows another detail of the arrangement of a catalyst support in a reactor as known in the art. As can be seen, there is a height difference between the upper side of the cassette and the lower side of the total arrangement. This height cannot be utilized for catalyst and is therefore an inactive part of the reactor which should be kept as small as possible to improve the efficiency of the reactor relative to the reactor volume. According to the present invention, this is achieved as can be seen in Fig. 7 by reducing the height of the cassette in the part which rests on the support i.e. the outer part of the cassette, while keeping the larger dimension in the centre section of the cassette where the full strength of the cassette is needed as explained earlier. The reduced overall dimension from the upper side of the cassette to the underside of the whole support structure can be utilized to increase the catalyst volume in the reactor and thereby the output of the reactor without compromising the strength of the catalyst support structure. The same is shown in Fig. 8 only in an isometric view which visualizes how a whole range of small beams in the grid of the cassette has this combined profile with decreased height near the support area and a larger height in the rest of the profile to maintain the catalyst support structures strength.

Claims

1 . Reactor for a catalytic process with one or more catalyst beds, comprising at least one support beam and support beam sealing means, a bottom support for each of said catalyst beds, the bottom support is constructed as a grid comprising a plurality of cassettes, each cassette is covered by a permeable screen with apertures large enough to allow flow through of process fluid, but small enough to retain the catalyst pellets, wherein a plurality of said cassettes comprises a protruding cassette sealing and said protruding cassette sealing co-operates with and seals with the support beam sealing means.

2. Reactor according to claim 1 , wherein said screen is removable fastened to said cassette.

3. Reactor according to any of the preceding claims, wherein the protruding cassette sealing is an integrated part of the screen.

4. Reactor according to any of the preceding claims, wherein the support beam sealing means is a protruding lip attached to the side of the support beam.

5. Reactor according to any of the preceding claims, wherein the protruding cassette sealing, and the support beam sealing means create a seal tight enough to retain the catalyst pellets.

6. Reactor according to any of the preceding claims, wherein the cross- sectional area of at least one of the cassettes grids is load optimized with a lower profile height in the ends of the cross sectional profile than in the middle of the cross sectional profile.

7. Reactor according to any of the preceding claims, wherein at least one of said cassettes comprises inspection ports.

8. Reactor according to any of the preceding claims, wherein the apertures of the screen each has an area of between 500 mm2 and 0,1 mm2.

9. Reactor according any of the claim 1 - 7, wherein the apertures of the screen each has an area of between 100 mm2 and 1 mm2.

10. Reactor according to any of the preceding claims, wherein the screen is made by woven wire mesh.

11. Reactor according to any of the claims 1 - 9, wherein the screen is made by welded wires and rods.

12. Reactor according to any of the claims 1 - 9, wherein the screen is made by a flat printed pattern.

13. Reactor according to any of the preceding claims, wherein the weight of the screen is below 100 kg.

14. Reactor according to any of the claims 1 - 12, wherein the weight of the screen is below 25 kg.

15. Reactor according to any of the preceding claims, wherein the screen is fixed to the cassette by means of quick release means, enabling the screen to be fixed to or detached from the cassette by hand or by hand tools.

16. Reactor according to any of the preceding claims, wherein the reactor is a hydroprocessing reactor, a hydrogenation reactor, a TIGAS reactor, or a methanation reactor.