CHEMICAL REACTOR WITH CATALYST SUPPORT SYSTEM
1. A chemical reactor holding a fixed bed catalyst, comprising a catalyst support system arranged in the lower part of the reactor for shielding at least one lower part reactor opening from said catalyst, the catalyst support system comprises flow channels to enable process fluid to flow to or from the reactor through said reactor opening, wherein the catalyst support system further comprises anti-blocking means to prevent blocking of said flow channels.
The invention relates to a chemical reactor comprising at least one catalyst support system and anti-blocking means arranged around and above a reactor opening, which prevents catalyst or other reactor parts to enter or exit a reactor opening.
- 1. A chemical reactor holding a fixed bed catalyst, comprising a catalyst support system arranged in the lower part of the reactor for shielding at least one lower part reactor opening from said catalyst, the catalyst support system comprises flow channels to enable process fluid to flow to or from the reactor through said reactor opening, wherein the catalyst support system further comprises anti-blocking means to prevent blocking of said flow channels.
The invention relates to a chemical reactor comprising a catalyst. More specifically, the invention relates to a catalyst support system arranged in the lower part of the chemical reactor to prevent the catalyst from entering and/or exiting the reactor through one or more process fluid openings in the reactor and it relates to arranging the catalyst support system with high strength.
Syngas is a mixture of hydrogen and carbon monoxide and it is produced by conversion of methane and other hydrocarbons with steam over a steam reforming catalyst through the steam methane reforming process in one form or another. In ammonia production tubular reforming is combined with secondary reforming and air is added to the secondary reformer to combust residual methane from the primary reformer and to adjust the syngas ratio to achieve the H2/N2 ratio of approx. 3.0 for the ammonia synthesis. When N2 is an undesired constituent in syngas, pure oxygen can be used as oxidant in the secondary reformer and this is the case in methanol plants. For methanol production a so-called “two-step reforming”-concept combining a tubular reformer with an oxygen-blown secondary reformer in the syngas section. The process lay-out includes adiabatic pre-reforming, tubular reforming and oxygen-blown secondary reforming. The oxygen acts as a source for internal process combustion of hydrocarbons coming from the tubular reformer. Operating conditions of the oxygen-blown secondary reformer are characterized by higher combustion temperatures than in air-fired lay-outs.
Another syngas technology is Autothermal reforming (ATR) which is a stand-alone process technology in which the tubular reformer is eliminated from the lay-out and pre-reformed natural gas is sent directly to an ATR reformer in which hydrocarbons are combusted by oxygen. By omitting the tubular reformer, the steam addition to the feedstreams can be reduced significantly.
For large-scale methanol plants, Autothermal reforming is today an alternative to two-step reforming technology for larger production capacity methanol plants of ie 5000 tpd.
ATR is a preferred technology for syngas manufacturing in GTL plants (Gas-to-Liquid) in which diesel is produced via Fischer-Tropsch (FT) synthesis. Syngas with H2/CO ratio of 2.0 can be produced directly with ATR reforming and such is especially suited for FT synthesis and production of FT liquids.
Operating conditions for the ATR reformer are even more severe than for oxygen blown secondary reformers and even more robust reactor layout are required for operation in ATR reformers. The steam-to-carbon feed ratio is lower and the combustion intensity and the flame temperature are much higher in ATR reformers.
The reactor design for ATR, oxygen-blown secondary reformers and air-blown secondary reformers comprises a burner, a combustion chamber, target tiles, a fixed catalyst bed, a catalyst bed support structure, a refractory lining, and a reactor pressure shell.
The catalyst bed support system serves both as structural support for the catalyst bed and as an outlet flow distributor guiding the syngas from the catalyst bed into the transfer line to the waste heat recovery system downstream the reformer. Such catalyst support systems have lay-outs that can be of various geometry, i.e. cone type structures, arch-type or dome type constructions. Dome and arch shaped catalyst support systems can suffer from failure and collapse. Cone type of catalyst support system has been used with good performance as catalyst support system, and failures and collapses with this type have not been observed. However, some degree of maintenance is generally reported to individual pieces of the ceramic elements and especially thin walled structural elements in vertical and/or horizontal direction.
The catalyst support system may be in contact with inerts for instance in the shape of spheres or lumps. These deliver forces onto the catalyst support system in points where stress levels can become excessive and initiate cracks which may result in failing of the bricks which the catalyst support system is made of.
Also the inerts block or partly block the flow area in the catalyst support system in the flow channels or in the inlet section of the channels, making the pressure drop over the support rise.
Known art offers little solution to this problem, as can be seen in the following references, where:
US2002071790 describes an integrated reactor for producing fuel gas for a fuel cell, the integrated reactor comprises a waste gas oxidizer (WGO) assembly having an associated WGO chamber, an inlet, an outlet and a flow path for exothermic gases produced in the WGO chamber. The integrated reactor has an auto-thermal reactor (ATR) assembly located within the WGO chamber. The ATR assembly has an inlet means and an outlet means for process gases flowing there through and a catalyst bed which is intermediate the inlet and outlet means. At least a part of the inlet means of the ATR assembly is located in the flow path of the WGO chamber to facilitate the transfer of thermal energy.
CN202606129 describes a non-metal high-temperature catalyst supporting piece. The catalyst supporting piece is arranged in a reactor and comprises a corundum brick support and a foamed ceramic plate arranged on the corundum brick support; and mounting contact surfaces of the corundum brick support and the foamed ceramic plate are saw-toothed; the corundum brick support is formed by integrally mortising at least two kinds of specially-shaped corundum bricks; mortar is filled in gaps among the specially-shaped corundum bricks; and ceramic fibre paper is filled in an annular gap between the corundum brick support and the inner wall of the reactor. The catalyst supporting piece has the characteristics of high temperature resistance, corrosion resistance, high mechanical strength, convenience in mounting, long service life and no catalyst leakage. The foamed ceramic plates of different specifications can selected according to the granular size of catalysts, and the tops of the corundum bricks contacted with the foamed ceramic plates have tooth-shaped structures, so that the smoothness of airflow is guaranteed; mortise structures are adopted by the corundum bricks, and the mortar is filled in the gaps among the corundum bricks, so that long-period running of equipment can be guaranteed; and the catalyst supporting piece is widely applied to chemical industry, pharmaceutical industry, petrochemical industry and the like.
None of the above known art references offer a solution to the problem of protecting a catalyst support system in a chemical reactor against damage and blockage by catalyst or other reactor particles.
Embodiments of the invention generally relate to a chemical reactor comprising a catalyst and a catalyst support system arranged in the lower part of the reactor. The catalyst support system shields at least one opening in the lower part of the reactor from the catalyst, to prevent the catalyst from access to the opening which may otherwise lead to the catalyst at least partly blocking the opening or exiting the reactor through the opening. It is however important that the catalyst support system does not block the opening, since fluid must be able to flow in or out of the opening. Also the pressure loss of the fluid through the catalyst support system is critical, a high pressure loss increases the demand on blowers/pumps and in the end increases the cost of running the chemical reactor. Therefore, the catalyst support system comprises flow channels which enables the process fluid to flow to or from the reactor through the reactor opening. The cross sectional flow area as well as the length of these flow channels influences the pressure loss for the fluid passing through the catalyst support system. It is important that the flow channels are not blocked by the catalyst or other parts in the reactor, since this may lead to an increase of the pressure loss for the process fluid passing through the catalyst support system. The catalyst support system is also vulnerable to mechanical damage where the catalyst or other reactor parts are in contact with the catalyst support system, especially the edges around the flow channels. Therefore, the catalyst support system further comprises anti-blocking means, arranged to prevent blocking of the flow channels and to prevent the catalyst or other reactor particles from damaging the catalyst support system. The anti-blocking means are constructed and arranged to ensure that the catalyst or other reactor parts cannot pass through the anti-blocking means and block the flow channels. They are also constructed and arranged to ensure that the catalyst or other reactor parts which do settle upon the anti-blocking means do not entail a critical rise in pressure loss.
In an embodiment of the invention, said anti-blocking means comprise a geometrical flow labyrinth with an outer face of the catalyst support system with a larger cross sectional flow area than the cross sectional flow area of the flow channels. This outer face is the surface upon which the catalyst or other reactor parts settles upon. Each contact point between this outer face and the catalysts or other parts may indeed partly block the catalyst support system which may lead to an increased pressure loss. But by having a larger cross sectional flow area of the outer face of the catalyst support system than the cross sectional flow area of the flow channels, it is ensured that this pressure loss is minimized and not critical.
More specifically, in an embodiment of the invention, the minimizing of the pressure loss is enabled by a cross sectional flow area of the outer face of the catalyst support system which is between 1.1 and 4.0 times larger than the total cross sectional flow area of the flow channels. Even more specifically, the cross sectional flow area of the outer face of the catalyst support system may be between 1.1 and 2.0 or even between 1.2 and 1.7 times larger than the total cross sectional flow area of the flow channels.
In an embodiment of the invention, the anti-blocking means comprises ramparts. The outer face of the catalyst support system is thus constructed with protruding members which are spaced apart, the space between the protruding members, the ramparts ensures sufficient cross sectional flow area of the anti-blocking means, while having a dimension which does not allow the catalyst or other reactor parts to pass through it. The ramparts have a construction and strength which protects against mechanical damage, which may otherwise occur in the contact with the catalyst or other reactor parts.
In a further embodiment of the invention, the catalyst support system may comprise a plurality of bricks, which when put together forms the catalyst support system. The flow channels are comprised in the catalyst support system and may either be internal flow channels in each or some of the bricks which then are hollow, flow channels formed by the outer geometry of the bricks when these are put together to form the catalyst support system, or both internal and external (relative to the bricks) formed flow channels. In an embodiment, the bricks comprise protrusions of any shape, in one embodiment more specifically brick legs and bricks shoulders, i.e. downwards or upwards and outwards protruding parts of the bricks and when put together side by side and on top of each other, the protruding parts of the bricks ensure the formation of flow channels between the bricks. Each brick may comprise a single leg or a plurality of brick legs and likewise, each brick may comprise one or a plurality of brick shoulders.
In an embodiment, said bricks are constructed to be arranged together to form an assembled catalyst support system in the form of a cone, dome, an arch, a cylinder, pyramid an inverted cone, a half doughnut or in a flat form, any shape which is constructional stable and serves the purpose best of protecting the catalyst or any other reactor parts from entering or exiting the reactor opening which the catalyst support system is arranged around and above, while keeping the pressure drop at an acceptable minimum and also preventing blocking of the catalyst support system flow channels. In an embodiment this is obtained by arranging the bricks in layers on top of each other.
Said anti-blocking means of the catalyst support system may in one embodiment be an integral part of the bricks, or they may in another embodiment be an extra independent part or layer which is arranged in connection to the outwards facing part of the bricks, i.e. the part of the bricks which are facing out towards the catalyst or other reactor parts, away from the reactor opening which the bricks are arranged above and around. Also an embodiment may combine anti-blocking means which are integrated with the bricks, with anti-blocking means which are independent parts arranged on the outside of said catalyst support system. In any case, the anti-blocking means may in an embodiment comprise oblong elements arranged perpendicular to the flow channels of the catalyst support system. These oblong elements may form continuous oblong anti-blocking means, such as for instance anti blocking rings or lines formed on the outside of the catalyst support system, with a distance between each continuous oblong element which allows for process fluid flow to the flow channels. The distance may be large enough to provide a cross sectional flow area which is larger than the cross sectional flow area of the flow channels, even when catalyst or other reactor elements are contacting and resting upon the anti-blocking means (and a partly blockage of the anti-blocking means cross sectional flow area is anticipated), but small enough to prevent said catalyst or other reactor parts to pass through the distance between the anti-blocking means. The specific distance between the anti-blocking means is adapted to the specific case, the larger the catalyst particles or other reactor parts are, the larger the distance may be. In a specific embodiment, the inert particle shape is the same size or larger than said distance between the anti-blocking means, the slot width, more specifically the inert particle size is 1.05-4.0, more specifically 1.8-3.5 times larger than the slot width.
In an alternative specific embodiment, the catalyst particle shape is the same size or larger than said distance between the anti-blocking means, the slot width, more specifically the catalyst particle size is 1.05-4.0, more specifically 1.1-1.7 times larger than the slot width.
In a specific embodiment, the anti-blocking means have a triangular cross-sectional shape with rounded corners of the triangle. While simple to produce, the triangular cross-sectional shape ensures constructional strength and the rounded corners minimizes the risk of fragmenting and cracking of the anti-blocking means as well as the risk of damage to the catalyst or other reactor parts which contact the anti-blocking means.
The mentioned other reactor parts may in an embodiment comprise inert elements or shaped catalyst particles arranged around and possibly also on top of the catalyst support system as a layer between the other catalyst particles and the catalyst support system, which are specially geometrically shaped to contact and support on the anti-blocking means while allowing process fluid flow through the gaps between the anti-blocking means and through the flow channels of the catalyst support system. An advantageous shape of these inert elements or shaped catalyst particles is in one embodiment a sphere, which is constructional stable and strong and which allows for sufficient process fluid flow, as the contact (and partly blocking) points between these spheres and the anti-blocking means are relative small compared to the free flow area between the spheres and between the spheres and the anti-blocking means. In a further embodiment, the geometrical shape may be a ring shape, which also ensures process fluid flow through the flow channels of the catalyst support system and in yet another embodiment, the inerts may be random shaped lumps.
Embodiments of the present invention are explained, by way of example, and with reference to the accompanying drawings. It is to be noted that the appended drawings illustrate only examples of embodiments of this invention and they are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
- 01. Catalyst support system
- 02. Brick
- 03. Brick leg
- 04. Brick shoulder
- 05. Flow channel
- 06. Anti-blocking means
- 07. Mono block
- 08. Brick layer
- 09. Sphere
A cross sectional view of the catalyst support system of
A cut sectional view (A) of the catalyst support system shown in
In the embodiments discussed above, the anti-blocking members are integrated with the bricks. A further embodiment as shown in
In the embodiment where the catalyst support system is cone shaped, the bricks may be slightly wedge-shaped as seen in
The above Figures are only some possible embodiments of the invention. Several other geometrical constructions of anti-blocking means are possible according to the invention, whereas some are shown in