WO2022008219A1

WO2022008219A1 - Catalytic reactor comprising an expandable structured packing

Info

Publication number: WO2022008219A1
Application number: PCT/EP2021/066850
Authority: WO
Inventors: Martin ØSTBERG; Henrik Guldberg Pedersen
Original assignee: Haldor Topsøe A/S
Priority date: 2020-07-10
Filing date: 2021-06-21
Publication date: 2022-01-13

Abstract

A reactor for catalytic reforming of a hydrocarbon gas comprises an expandable structured packing arranged within an outer casing of the reactor; despite being rigid, the expandable structured packing is able to adjust to the dimensions of the outer casing, even when these are changing due to temperature and pressure changes, keeping the gas flow and pressure constant.

Description

CATALYTIC REACTOR COMPRISING AN EXPANDABLE STRUCTURED PACKING.

FIELD OF THE INVENTION

The present invention concerns a reactor for catalytic re forming of a hydrocarbon gas, the reactor comprises an ex pandable structured packing, in particular an expandable structured packing comprising catalyst.

BACKGROUND OF THE INVENTION

The present invention relates to a reactor for reforming of a hydrocarbon gas comprising a structured packing, e.g. a monolith, which is expandable. The expansion is not ob tained by flexibility of the material (e.g. by elastic or plastic deformation of the material) from which the struc ture is made of. This means that the expansion and contrac tion can be obtained also when the structured packing is made from rigid materials, such as ceramics or metal.

If the expandable structured packing is inserted in a tube (or another container), the structured packing will expand to fill out the tube. It may leave a predetermined gap be tween the inner tube wall and the outer part of the struc tured packing. If the diameter of the tube changes, the structured packing will adjust to the new inner diameter of the tube, and in case there is a predetermined gap, the structured packing will adjust to maintain the predeter mined gap. A diameter change (increase) can for example oc cur when operating reactors (which have the structured packing within, or within its reactor tubes) at high tem peratures and pressure. An example is steam reforming of hydrocarbons to produce H2 and CO. This process occurs in tubular reactors at high temperature and pressure, and it is well known that the tube diameter grows over time, espe cially in the hottest part. The properties of the expanda ble structured packing according to this invention may be used for monolith structures in a steam reformer and other catalytic reactors, but the invention also applies to other structures, processes, reactor shapes etc.

In the following, the invention will be explained using steam reforming as an example, but it is to be understood that the invention can be used for other processes, reac tors etc. as mentioned above. A steam reformer (tubular re former) comprises a number of tubes, which are externally heated. Inside the tubes, the hydrocarbon gas is reacted to form the desired products. The reaction is catalytic, and normally the tubes contains catalyst pellets. The reaction is highly endothermic, hence large amounts of heat must be transported to the interior of the tube. The heat transfer is to a large degree determined by the size and shape of the catalyst pellets. An alternative to catalyst pellets is a monolith, which can be made to have a better performance with respect to heat transfer and the resulting pressure drop.

The ability of the monolith to maintain a predetermined gap, is a parameter which influences the performance of the monolith. A conventional monolith, not build according to this invention, will not expand, when the reformer tube ex pands, and the gap between the inner tube wall and the out- er part of the monolith will increase, which will influence the heat transfer properties negative.

Accordingly, there is a need for a reactor for catalytic reforming of hydrocarbon gas comprising an expandable structured packing, which is made from a solid structure, but can adapt to changes in the inner dimensions of the re actor. Further, there is a need for a reactor for catalytic reforming of hydrocarbon gas comprising an expandable structured packing which can maintain a predetermined gap between the inner reactor wall and the expandable struc tured packing. This is solved by a reactor for catalytic reforming of hydrocarbon gas comprising an expandable structured packing according to the present invention.

SUMMARY OF THE INVENTION

In a reactor for catalytic reforming of a hydrocarbon gas and comprising an expandable structured packing, the ex pandable structured packing (for instance a monolith struc ture) according to the present invention, has the function that it can expand, and at the same time, block the flow of process fluid, which would otherwise bypass through the ex pansion openings that are created when the expandable structured packing is expanded. This means that the expand able structured packing can retain its performance with re spect to heat transfer, also when the tube around it ex pands. Also, the expansion can be used to obtain the prede termined gap in tubes that from the start have slightly different diameters. In an embodiment of the invention, a reactor for catalytic reforming of a hydrocarbon gas comprises an outer casing with a longitudinal central axis. In most cases, the outer casing will have a cylindrical shape apart from the top and bottom endcaps, but the present invention also applies, should the outer casing have other shapes. The reactor fur ther comprises means for directing a feed hydrocarbon gas into the reactor at an inlet end and through the reactor and means for directing a reformed product hydrocarbon gas out of the reactor at an outlet end. These inlet and outlet means may have any shape as known in the art, e.g. compris ing tubes with flange connections or other known art solu tions. Furthermore, the reactor comprises an expandable structured packing disposed within the outer casing. The expandable structured packing is made of a rigid material and has a design which allows the expandable structured packing to be reversibly movable in a plurality of "angled packing directions". Hence, the expandable structured pack ing does not have to be flexible to adapt to any changes in the inner dimensions of the outer casing, it adapts via movement relative to the central axis, i.e. movement adapted to the movement of the inner dimensions of the out er casing. The angled packing directions are radially away from the central axis (i.e. outwards away from the central axis and towards the inner side of the outer casing), and the angled packing directions are downwards relative to the outer casing. Hence, the angled packing directions are both radially away/outwards from the central axis and downwards relative to the outer casing. This described reversible movement of the expandable structured packing in the angled packing directions has the effect that the expandable structured packing is kept in close contact with the inte- rior surface of the outer casing; the expandable structured packing follows the movements of the interior surface of the outer casing due to heat expansion, creep or the like and thus allows for the use of a rigid material in much larger scale than pellets, e.g. monolith, without compro mising the heat exchange and the performance of the cata lytic reactor. Furthermore, the expandable structured pack ing has a design which enables movement of the hydrocarbon gas through the expandable structured packing. This may be achieved in any way as known in the art, for instance by channels or ducts in the expandable structured packing, by a porous structure of the expandable structured packing, by folded patterns of the expandable structured packing etc. The expandable structured packing may comprise at least one module, and each of the modules comprises a plurality of first elements and at least one second element. The first elements of the module(s) are arranged in a circular pat tern around the central axis. It is to be understood that the first elements, when arranged close together in the circular pattern, may in one embodiment form a void around the central axis; or they may in another embodiment be con structed to close fit and leave no space or almost no space in the centre area around the central axis, again with res ervation to inaccuracies and tolerances as are practical possible and feasible. Furthermore, the first elements com prise sliding means. These sliding means are adapted to in- ter-act with the at least one second element of each mod ule, to force the first elements in the angled packing di rections by means of gravity. Hence, the first elements are arranged on top of the one or more second elements and slide relative to the second elements in the angled packing directions to respond to any dimensional changes of the in- ner surface of the outer casing, which has the effect that close contact is kept between the expandable structured packing and the inner surface of the outer casing at all times/conditions, ensuring the optimal heat exchange be tween the outer casing and the hydrocarbon gas (it is to be understood that by "hydrocarbon gas" is meant all of the following: the feed hydrocarbon gas which is fed into the reactor, the partially reformed hydrocarbon gas flowing in the reactor and the reformed product hydrocarbon gas flow ing out of the reactor). The at least one second element of each module may comprise a top surface with an angle adapted to inter-act with the sliding means of the plurali ty of first elements of each module, when the expandable structured packing is installed in the reactor. When the top surface of the second element(s) has the same angle as the bottom surface of the first elements, good sliding in teraction is ensured, and the inner volume of the reactor is utilized optimally with active reforming catalytic mate rial, and the risk of the hydrocarbon gas by-passing the catalytic material is lowered.

In an embodiment of the invention the central axis of the outer casing is vertical. It is to be understood that by vertical is meant any position as close to vertical as is normal practice in construction of process equipment and buildings with the inaccuracies and tolerances which are common.

In a further embodiment of the invention, the expandable structured packing comprises one or more ceramic monoliths. One of the advantages of the present invention is that it allows the use of rigid material for the expandable struc- tured packing while still being able to adapt to change in dimensions of the reactor outer casing. It is therefore to be understood that the expandable structured packing can be any suitable rigid material also including metal and the combination of metal and ceramics.

In an embodiment of the invention, the sliding means com prise a bottom surface of the first elements of each module with an angle between 1 - 89 degrees, preferably 30 to 86 degrees to the central axis, when the expandable structured packing is installed in the reactor. This angled bottom surface of the first elements enables the first elements to slide outwards, away from the central axis and downwards in the angled packing directions by the force of gravity. It is to be understood that the angle of the bottom surface is to be adapted to each different case / reactor as it is de pendent on the weight of the first elements, the friction between the first elements and the one or more second ele ments and other specific conditions; the angle is adapted to ensure that the expandable structured packing responds to dimensional changes of the reactor outer casings inner surface. Also, the sliding means may be combined with guides or rails in the expandable structured packing, for instance between the first and second elements, to control the movement of the expandable structured packing.

To ensure an effective pass of the hydrocarbon gas through the reactor, in an embodiment the expandable structured packing is designed to direct the hydrocarbon gas through the expandable structured packing in an angled gas direc tion. The angled gas direction is partly radial to and away from the central axis towards the inner surface of the out- er casing and partly downwards or upwards relative to the reactor. The effect is that the hydrocarbon gas will per form a zig-zag movement between the heat demanding expanda ble structured packing surface where the reforming is per formed and the heat providing inner surface of the outer casing, either an upward zig-zag movement or a downward zig-zag movement. The movement of the hydrocarbon gas back towards the central axis, away from the inner surface of the outer casing may be enabled by by-pass between the ex pandable structured packing or, in another embodiment of the invention by the expandable structured packing being arranged or designed to allow or direct the hydrocarbon gas in a direction away from the inner surface of the outer casing and towards the central axis.

In an embodiment of the invention the expandable structured packing has a catalytic material coated onto at least a part of its surface. The surface of the expandable struc tured packing may be of any suitable kind as known in the art for carrying a catalyst, such as corrugated plate, po rous ceramics with integrated voids and passages, rolled corrugated substrate to mention some but not all. The cata lysed coating on the surface of the expandable structured packing enables the hydrocarbon gas to be reformed when passing through or along the expandable structured packing within the reactor.

In an embodiment of the invention, the expandable struc tured packing is at least partly disposed in an annular zone along the inner periphery of the outer casing. In this embodiment, as also described in an earlier embodiment, the expandable structured packing leaves a void in the central part of the reactor along the central axis. The reactor further comprises a packed bed of catalyst pellets disposed in a core zone surrounding the central axis. The outer pe riphery of the core zone contacts the inner periphery of the annular zone. Hence, in this embodiment the invention combines the known art reactor with catalyst pellets in an inner zone of the reactor with an expandable structured packing in an outer annular zone which surrounds the cata lyst pellets. In an embodiment of the invention, the annu lar zone and the core zone is separated by a perforated wall. This has the effect that the catalyst pellets are controlled and kept in the core zone by the perforated wall to avoid that they block gas passages or movement of the expandable structured packing.

In an embodiment of the invention the movement of the ex pandable structured packing in the angled packing direc tions is at least partly driven by the pressured performed by the catalyst pellets in a radial direction caused by gravitational force on the pellets. In a further embodiment the movement of the expandable structured packing in the angled packing directions is at least partly driven by pressure from the hydrocarbon gas moving through the reac tor. In a further embodiment of the invention, the movement of the expandable structured packing is at least partly driven by pressure from loaded springs. It is to be under stood that apart from the described movement of the expand able structured packing in an angled packing direction, there is also a reversible movement when the outer shell dimension is not enlarging but contracting. Accordingly, it is to be understood that this counter movement of the ex- pandable structured packing is driven by the contractional forces of the outer shell.

To avoid the hydrocarbon gas from by-passing the expandable structured packing, in an embodiment of the invention the reactor comprises sealing means. The sealing means may be integrated in the expandable structured packing. As the ex pandable structured packing expands, voids forms and also expands and the sealing means blocks these voids at least partly to avoid the hydrocarbon gas from by-passing the ex pandable structured packing which otherwise would decrease the performance of the reactor. In an embodiment, these sealing means may comprise elements inserted in slots of the expandable structured packing which are adapted to slide in said slots. This has the effect that the interac tion between the elements, slots and the expandable struc tured packing results in a labyrinth sealing between the moving parts of the expandable structured packing.

FEATURES OF THE INVENTION

1. A reactor for catalytic reforming of a hydrocarbon gas comprising a) an outer casing having a longitudinal central axis, b)means for directing a feed hydrocarbon gas into the reactor at an inlet end and through the reactor and means for directing a reformed product hydrocarbon gas out of the reactor at an outlet end, c) an expandable structured packing disposed within the outer casing, wherein the expandable structured packing is composed of a rigid material with a structure designed so as to allow the expandable structured packing to be reversibly movable in a plurality of angled packing directions partly radi al to and away from the central axis and partly downwards relative to the outer casing so as to keep the expandable structured packing in close contact with the interior surface of the outer cas ing, and wherein the expandable structured packing has a design so as to enable movement of the hydro carbon gas through the expandable structured pack ing, the expandable structured packing comprises at least one module, each module comprises a plurality of first elements arranged in a circular pattern around the central axis and comprising sliding means adapted to inter-act with at least one second element of each module to force the first elements in the angled packing directions by means of gravi ty, the at least one second element of each module comprises a top surface with an angle adapted to inter-act with the sliding means of the plurality of first elements of each module when the expanda ble structured packing is installed in the reactor.

2. Reactor according to feature 1, wherein the longitudinal central axis of the outer casing is in a vertical position.

3. Reactor according to any of the preceding features, wherein the expandable structured packing comprises one or more ceramic monoliths.

4. A reactor according to any of the preceding features, wherein the sliding means comprise a bottom surface of the first elements of each module with an angle between 1 - 89 degrees, preferably 30 - 86 degrees to the central axis when the expandable structured packing is installed in the reactor.

5. A reactor according to any of the preceding features, wherein the expandable structured packing comprises a de sign so as to enable movement of the hydrocarbon gas through the expandable structured packing in an angled gas direction partly radial to and away from the central axis towards the inner surface of the outer casing and partly downwards or upwards relative to the reactor.

6. A reactor according to any of the preceding features, wherein the expandable structured packing is arranged to allow the hydrocarbon gas to move in a direction away from the inner surface of the outer casing and towards the cen tral axis. 7. Reactor according to any of the preceding features, wherein the expandable structured packing has a catalytic material coated onto at least a part of its surface.

8. A reactor according to any of the preceding features, wherein the expandable structured packing is at least part ly disposed in an annular zone along the inner surface of the outer casing, the reactor further comprises a packed bed of catalyst pellets disposed in a core zone surrounding the central axis, wherein the outer surface of the core zone contacts the inner surface of the annular zone.

9. Reactor according to feature 8, wherein the angled pack ing directions movement of the expandable structured pack ing is driven by a pressure from the catalyst pellets in a radial direction caused by gravitational force on the pel lets and by pressure from the hydrocarbon gas moving through the reactor.

10. Reactor according to any of the features 7 - 9, wherein the annular zone and the core zone is separated by a perfo rated wall.

11. Reactor according to any of the preceding features com prising sealing means to prevent hydrocarbon gas from by passing the expandable structured packing.

12. Reactor according to feature 11, wherein the sealing means comprise elements inserted in slots of the expandable structured packing and adapted to slide in said slots. 13. Reactor according to any of the preceding features, wherein the angled packing directions movement of the ex pandable structured packing is driven by a pressure from loaded springs.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed description of the invention will be appar ent from the following description of a specific embodiment with reference to the following principle drawings in which:

Fig. 1 shows a side cut view of an expandable structured packing according to a specific embodiment of the inven tion,

Fig. 2 shows a top view of an expandable structured packing according to a specific embodiment of the invention,

Fig. 3 shows a top view of an expandable structured packing according to a specific embodiment of the invention,

Fig. 4 shows a top view of an expandable structured packing according to a specific embodiment of the invention,

Fig. 5 shows a top view of a detail of an expandable struc- tured packing according to a specific embodiment of the in vention,

Fig. 6 shows a top view of a detail of an expandable struc tured packing according to a specific embodiment of the in vention . POSITION NUMBERS

01. Expandable structured packing.

02. Ceramic monolith.

03. Module.

04. First element.

05. Sliding means.

06. Second element.

07. Second element top surface.

08. Angled packing directions.

09. Sealing means.

10. Slot.

11. Spacer.

DETAILED DESCRIPTION OF THE DRAWINGS

In Fig. 1 a specific embodiment of the expandable struc tured packing 01 to be comprised in a reactor (not shown) for catalytic reforming of a hydrocarbon gas is shown seen from the side of a cut down through the diameter of the ex pandable structured packing. In this embodiment the expand able structured packing is a ceramic monolith 02 in the form of a module 03 with an outer cylindrical shape. It is to be understood that a reactor according to the invention may comprise several modules, for instance stacked on top of each other or with voids in between the modules. The module as seen in the side cut view in Fig. 1 comprises a number of first elements 04 (two can be seen) and one sec ond element 06. The first elements comprise sliding means 05 which in the embodiment shown comprise a bottom surface with an angle between 30 and 86 degrees to the central axis on each of the first elements. To more clearly explain the elements and function, Fig. 1 shows the elements with clearance in between. In reality, the first elements slid ing means will rest on the second element top surface 07 which also has an angle between 30 and 86 degrees to the central axis. If the expandable structured packing is in stalled in a reactor with an outer casing having an inner diameter which is larger than the outer diameter formed by the first elements, the first elements will each slide downwards and radially outwards in an angled packing direc tion 08 each, on the sliding means as an effect of gravity, until the first elements reach the inner surface of the outer casing.

As can be seen on Fig. 3, a top view of a module comprising eight first elements, a distance between the first elements will form and grow as the first elements slide down- and radially outwards in each of their angled packing direc tions. To avoid a by-pass of the hydrocarbon gas between the first elements, an embodiment is shown in Fig. 2, where sealing means 09 in the shape of plates are arranged be tween each of the first elements in slots 10. As the dis tance between the first elements forms and grows, the seal ing means are able to slide within the slots, where they form a blocking of the by-pass that would otherwise form between the first elements.

Fig. 5 and Fig. 6 shows a further embodiment, where the sealing means are integrated in each one first elements as a protrusion which has a sliding fit with a slot in an ad jacent first element, thereby also forming a blocking of the potential by-pass for the hydrocarbon gas. It is to be understood that the sealing means may be formed by further forms and elements. It may be beneficial to arrange the sealing means close to the periphery of the module, for maximum flow blocking effect. The sliding means are shown to be plane in these embodiments, but they may also be curved. Furthermore, it is to be understood that the number of first and second elements may vary as best fit for the reactor and process, and the dimensions, positions and an gles may be adjusted to the specific demands for each reac- tor and process parameters.

It may be important for the function of the process, for the flow of the hydrocarbon gas within the reactor - that a desired gap between the inner surface of the outer casing and the expandable structured packing is maintained. For that purpose, an embodiment is shown in Fig. 4, where each first elements are equipped with spacers 11. The spacers ensure that the first elements will not slide all the way to the inner surface of the outer casing when the inner di- ameter of the outer casing is changing. A constant gap is maintained between the outer casing and the expandable structured packing and a constant volume for the hydrocar bon gas to flow in is ensured, thereby keeping the gas flow and pressure difference stable even though the dimensions of the outer casing is changing.

Claims

1. A reactor for catalytic reforming of a hydrocarbon gas comprising d) an outer casing having a longitudinal central axis, e) means for directing a feed hydrocarbon gas into the reactor at an inlet end and through the reactor and means for directing a reformed product hydrocarbon gas out of the reactor at an outlet end, f) an expandable structured packing disposed within the outer casing, wherein the expandable structured packing is composed of a rigid material with a structure designed so as to allow the expandable structured packing to be reversibly movable in a plurality of angled packing directions partly radi al to and away from the central axis and partly downwards relative to the outer casing so as to keep the expandable structured packing in close contact with the interior surface of the outer cas ing, and wherein the expandable structured packing has a design so as to enable movement of the hydro carbon gas through the expandable structured pack ing, the expandable structured packing comprises at least one module, each module comprises a plurality of first elements arranged in a circular pattern around the central axis and comprising sliding means adapted to inter-act with at least one second element of each module to force the first elements in the angled packing directions by means of gravi ty, the at least one second element of each module comprises a top surface with an angle adapted to inter-act with the sliding means of the plurality of first elements of each module when the expanda ble structured packing is installed in the reactor.

2. Reactor according to claim 1, wherein the longitudinal central axis of the outer casing is in a vertical position.

3. Reactor according to any of the preceding claims, where in the expandable structured packing comprises one or more ceramic monoliths.

4. A reactor according to any of the preceding claims, wherein the sliding means comprise a bottom surface of the first elements of each module with an angle between 1 - 89 degrees, preferably 30 - 86 degrees to the central axis when the expandable structured packing is installed in the reactor.

5. A reactor according to any of the preceding claims, wherein the expandable structured packing comprises a de sign so as to enable movement of the hydrocarbon gas through the expandable structured packing in an angled gas direction partly radial to and away from the central axis towards the inner surface of the outer casing and partly downwards or upwards relative to the reactor.

6. A reactor according to any of the preceding claims, wherein the expandable structured packing is arranged to allow the hydrocarbon gas to move in a direction away from the inner surface of the outer casing and towards the cen tral axis.

7. Reactor according to any of the preceding claims, where in the expandable structured packing has a catalytic mate rial coated onto at least a part of its surface.

8. A reactor according to any of the preceding claims, wherein the expandable structured packing is at least part ly disposed in an annular zone along the inner surface of the outer casing, the reactor further comprises a packed bed of catalyst pellets disposed in a core zone surrounding the central axis, wherein the outer surface of the core zone contacts the inner surface of the annular zone.

9. Reactor according to claim 8, wherein the angled packing directions movement of the expandable structured packing is driven by a pressure from the catalyst pellets in a radial direction caused by gravitational force on the pellets and by pressure from the hydrocarbon gas moving through the re actor.

10. Reactor according to any of the claims 7 - 9, wherein the annular zone and the core zone is separated by a perfo rated wall.

11. Reactor according to any of the preceding claims com prising sealing means to prevent hydrocarbon gas from by passing the expandable structured packing.

12. Reactor according to claim 11, wherein the sealing means comprise elements inserted in slots of the expandable structured packing and adapted to slide in said slots.

13. Reactor according to any of the preceding claims, wherein the angled packing directions movement of the ex pandable structured packing is driven by a pressure from loaded springs.