Cascade reactor system and method for carrying out an endothermic reaction

Abstract

The invention related to a cascaded reactor system (10) and a method for carrying out an endothermic reaction from a fed reactive mixture stream characterized in that comprising a plurality of reactor shells (20) serially connected each having at least one reactive stream duct (22), a stream inlet (25) for receiving the fed reactive mixture stream, a stream outlet (26), a catalyst section (21) provided inside said reactive stream duct (22) between said stream inlet (25) and stream outlet (26), an insulation filling (60) at least partly encompassing said reactive stream duct (22), a ceramic catalyst bed (30) accommodated in said catalyst section (21), where the reactive mixture stream undergoing a catalytic reaction, electrical heating means (40) for heating said structured ceramic catalyst bed (30) up to a predetermined reaction temperature, at least two electrical feeds (51) passing through the inlet section connected to an electrical power supply (50) provided outside of the reactive stream duct (22), wherein the inlet section of at least one pressure vessel contains a separating device for creating a cold section within the inlet zone of said reactor shell (20).

Description

[0001] DESCRIPTION

[0002] CASCADE REACTOR SYSTEM AND METHOD FOR CARRYING OUT AN ENDOTHERMIC REACTION

[0003] TECHNICAL FIELD

[0004] The invention relates to an electrically heated cascaded reactor system for completing an endothermic reaction from a fed reactive mixture stream and a method thereof.

[0005] PRIOR ART

[0006] Typical high temperature endothermic processes employ heat generated via the combustion of a fuel. For example, steam methane reforming involves a hydrocarbon-steam mixture which flows through reactor tubes containing Ni-based catalyst pellets. The necessary heat for the high-temperature reaction is generated in the surroundings of the reactor tubes using burners. The generated heat is then transfer, mostly by radiation, across the wall of the reactor tubes. Such configuration is commonly known in industry as fired furnace or fired box. This technology is state of the art in processes like steam methane reforming, steam cracking, reverse water gas shift, and ammonia cracking. Limitations of this approach lie in the low efficiency of the firebox itself, the production of emissions via flue gases from the burners and the limited maximum operating temperature, which is determined by the mechanical stability of the tube material.

[0007] Electrically heated reactors present solutions to the described limitations of conventional fired furnaces. Additionally, the source of heating can be completely decarbonized when fossil fuel is replaced by renewable electricity.

[0008] Several reactor systems for direct electric heating are disclosed in literature (eg.: EP3895795, EP3574991A1), most of them using resistive heating for heat generation.

[0009] EP3895795 for example, introduces a reactor with an electrically heated structured ceramic catalyst having hollow flow paths within where the reactive mixture stream is flowing. The resistive heating elements incorporated within these paths generate the heat necessary to power endothermic reactions. A preferred design features coaxial wire heaters, possibly meandering through multiple paths. In EP3574991A1 , a metallic macrostructure is coated with catalytically active material and heated by directing electricity through this metallic macrostructure. The generated heat is directly consumed by the catalyst to complete an endothermic reaction.

[0010] For processes where high outlet temperatures are required, temperatures of the heating means can rise up to 1200°C, which will cause thermal expansion on the heating means, independent of being a wire, a metallic monolith or metal foam. This, combined with the reduced mechanical properties of the conductive material at high temperatures, increase the risk of mechanical deformation, failure and potential electrical shorts due to unwanted contacting of the heating means. This problem increases in severity with the length of the electrically heated bed.

[0011] Shorter electrically heated beds reduce expansion problems, which is often problematic for washcoated electrically heated beds, but at the same time require larger cross-sections to maintain an adequate catalyst volume for large scale reactor systems. Larger cross-sections on the other hand provide challenges in distributing the flow evenly across the whole catalytic bed, which is crucial to avoid hotspot formation and uneven conversion of the reactive mixture stream across the bed. Especially for endothermic reactions, the heat consumption is strongly dependent on the molecules converted. Additionally, the electrical heating means provides an even heat generation throughout the entire bed. Small deviations in flow distribution can therefore have a huge influence on the temperature profile and uniformity within the catalyst bed.

[0012] Thus, it is required to provide a solution that solves the mentioned objective technical problems while designing a system that involves an electrically heated structured ceramic catalyst and is used to carry out a high temperature endothermic reaction.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] The present invention relates to an electrically heated cascaded reactor system and a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0015] An object of the present invention is to provide a reactor system that allows to modularly increase the capacity of a single train by in series connection of individual reactors. Another object of the invention is to provide a cascaded reactor system that reduces the heat exposure of electrical feeds that power the electrical heating means.

[0016] Another object of the invention is to provide a cascaded reactor system that reduces the mechanical deformation and prevents the shortcutting of electric heating means.

[0017] Another object of the invention is to provide a cascaded reactor system that reduces uneven distribution of reactive mixture stream passing through the electrically heated catalytic bed, thus avoiding hotspot formation within said electrically heated catalytic bed.

[0018] In order to achieve the above mentioned objects or those disclosed or to be deducted from the detailed description, the present invention relates to a reactor system for the production of carbon dioxide, synthesis gas, and hydrogen from a stream comprising a mixture of a nebulized liquid and / or gas hydrocarbon and / or methane-containing, and / or of a water steam, and / or of an oxidant stream and / or carbon dioxide and / or hydrogen and / or ammonia and / or volatile organic compounds (VOC) comprising at least two electrically heated reactors connected in series so that the outlet stream of the prior electrically heated reactor directly enters to the inlet section of the following electrically heated reactor.

[0019] Thus, the invention is a cascaded reactor system to carry out an endothermic reaction of a reactive mixture stream to be converted to a product gas or product stream characterized in that comprising

[0020] - at least two reactor shells connected in series, so that a stream outlet of a first reactor shell is directly connected to a reactor inlet of a second reactor shell and,

[0021] - where each reactor shell comprises at least one reactive stream duct, the stream inlet for receiving the fed reactive mixture stream, the stream outlet, a catalyst section provided inside said reactive stream duct between said stream inlet and stream outlet; an insulation filling at least partly encompassing said reactive stream duct, a catalyst bed accommodated in said catalyst section, where the reactive mixture stream undergoes a catalytic reaction, electrical heating means for heating said ceramic catalyst bed up to a predetermined reaction temperature; at least two electrical feeds passing through the inlet section connected to an electrical power supply provided outside of the reactive stream duct, and

[0022] - wherein the stream inlet of at least one reactor shell contains a separating device for creating a cold section within the inlet zone of said reactor shell wherein the electric feeds that bring electricity into the reactor shell are at least partly located within said cold section for preventing said electric feeds from exposition to high temperatures. Thus, a modular system is provided having reduced heat exposure to electrical connections.

[0023] Another object of the present invention refers to a method for carrying out an endothermic reaction using a cascaded reactor system such as in claims 1-9 characterized in that comprising the steps of:

[0024] - operating power supply for providing electrical energy to the electrically heating means in each reactor shell of the cascaded reactor system,

[0025] - feeding reactive mixture stream to stream inlet of a first reactor shell in the series.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a drawing illustrating sectional view of the system.

[0028] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0029] 10 Cascaded reactor system

[0030] 20 Reactor shell

[0031] 21 Catalyst section

[0032] 22 Reactive stream duct

[0033] 25 Stream inlet

[0034] 26 Stream outlet

[0035] 27 Flanged or welded connection

[0036] 28 Inlet chamber

[0037] 281 cold section

[0038] 282 separating device

[0039] 29 Sealed flange

[0040] 30 Ceramic catalyst bed

[0041] 31 Hollow flow path

[0042] 40 Electrical heating means

[0043] 41 Meandered sections

[0044] 50 Power supply

[0045] 51 Electrical feeds

[0046] 52 Conducting bars

[0047] 60 Insulation filling DETAILED DESCRIPTION OF THE INVENTION

[0048] Turning to the invention in more detail, it is provided a reactor system and a method for the production of carbon dioxide, synthesis gas, and hydrogen from a stream comprising a mixture of a nebulized liquid and / or gas hydrocarbon and / or methane-containing, and / or of a water steam, and / or of an oxidant stream and / or carbon dioxide and / or hydrogen and / or ammonia and / or volatile organic compounds (VOC). More specifically the present invention refers to a cascade reactor system comprising multiple reactor shells connected in series, each hosting an electrically heated structured ceramic catalyst and a compliant method for using this configuration for steam methane reforming process and / or dry reforming process and / or partial oxidation process and / or reverse water gas shift process and / or ammonia cracking and / or dehydrogenation reactions.

[0049] The outlet section of a previous electrically heated reactor and the inlet section of the subsequent electrically heated reactor in series are connected together by flanges or welding. The advantage of this configuration, with respect to a hypothetical configuration in which there are multiple catalytic sections allocated in series in a single pressure vessel, is that next to the inlet gas section, a ‘cold section’ with temperatures below 500°C can be realized, in which it is possible to allocate the connections between the power supply and the electric heating means (see FIG. 1). Without this cold section, the electrical conductors and electrical connections could face temperatures of up to 1200 °C. These temperatures not only demand materials with high temperature stability, but also cause problems regarding corrosion, metal dusting and hydrogen embrittlement and in general reduce the lifetime of such connections dramatically compared to connections allocated within a cold section. Therefore, the implementation of a cold section at the inlet of at least one pressure vessel is the distinct feature that enables an in series assembly of electrically heated pressure vessels.

[0050] Having said this, an in series configuration of electrically heated reactors offers many advantages compared to a single pressure vessel containing a single electrically heated bed at same production capacity.

[0051] The length of the electrically heated structured ceramic catalyst bed is designed to avoid excessive thermal expansion of the electric heating means, which may lead to electrical short cut of the electrical heating means itself or even with downstream equipment. The length of the electrically heated structure catalyst bed is preferably between 100 mm and 2000 mm, more preferably between 200 mm and 1000 mm. Increasing the production capacity within a single electrically heated bed therefore typically involves an increase in cross section, and not in length of the electrically heated catalytic bed.

[0052] In order to avoid hot spots or slip of unconverted reactive mixture through the electrically heated catalytic bed, a uniform flow distribution throughout the electrically heated catalytic bed is required. In order to achieve this, two factors need to be taken into account:

[0053] 1) Cross section of the electrically heated catalytic bed. A smaller cross section facilitates the uniform distribution of the inlet stream entering in the electrically heated catalytic bed.

[0054] 2) Pressure drop within the electrically heated catalytic bed. A larger pressure drop facilitates the uniform distribution of the inlet stream within the electrically heated catalytic bed. This can be realized by a higher gas velocity flowing through the electrically heated catalytic bed.

[0055] For both mentioned factors, it is beneficial to divide a large single catalytic bed into multiple smaller ones positioned in series. For the same gas feed normalized to the overall catalytic bed volume, the linear gas velocity within the in series configuration will be much higher, thus resulting in an higher pressure drop and therefore a more homogenous gas distribution within the bed.

[0056] It should be noted that the pressure drop within an electrically heated catalytic bed is typically very small, which leads to challenges for avoiding maldistribution.

[0057] Referring to figure 1 , the cascaded reactor system (10) comprises a plurality of reactor shells (20). Each reactor shell (20) comprises at least a stream inlet (25) and at least a stream outlet (26). Each reactor shell (20) comprises a reactive stream duct (22) provided between said stream inlet (25) and said stream outlet (26). Said stream duct is encompassed by an insulation filling (60).

[0058] Each reactor shell (20) comprises a catalyst section (21) provided inside said reactive stream duct (22).

[0059] The catalyst section (21) comprises a structured ceramic catalyst bed (30) comprising a plurality of hollow flow paths (31) which are configured to allow the reactive mixture stream to pass through and coming in physical contact with the inner walls of the hollow flow paths (31) of the structured ceramic catalyst bed (30). The catalyst section (21) comprises electrical heating means (40) for heating said structured ceramic catalyst bed (30) up to a predetermined reaction temperature. At least two electrical feeds (51) passing through the inlet section connected to an electrical power supply (50) provided outside of the reactive stream duct (22). A separating device is installed within the inlet section, creating a cold section (281), which is hosting the electrical connections between electric feeds and heating means. Providing electrical feeds (51) in the cold section significantly reduces heat exposure of electrical feeds (51).

[0060] Thanks to the arrangement of the cascaded reactor system (10) it is possible to connect the electrical heating means (41) to the electrical feeds (51) in the cold section (281) of the reactor shells (20) which is the coldest part of the reacting stream duct (22). This, reduces he risk of failure, the need of maintenance and increases the lifetime of the connections between the electrical heating means (41) and the electrical feeds (51).

[0061] Reactor shells (20) are serially connected where the stream outlet (26) of a reactor shell (20) is connected to the stream inlet (25) of the next reactor shell (20). This provides, a continuous duct allowing reactive mixture stream to pass through starting from the stream inlet (25) of a first reactor shell (20) in series to the stream outlet (26) of the last reactor shell (20) in series. This allows to modularly increase the number of reactor shells (20) in order to increase production capacity, while maintaining a short length of the structured ceramic catalyst bed (30).

[0062] Connections between reactor shells (20) may be provided by flanges or welding. Thus a flanged or welded connection (27) is provided between subsequent reactor shells (20).

[0063] Modularly increasing the number of reactor shells (20) allows to partially compensate for a possible malfunctioning of one individual reactor shell (20) in series by separately controlling the power supplied to each unit.

[0064] Stream outlet (26) and stream inlet (25) of each reactor shell (20), is arranged in such way that reactor shells (20) can be serially connected. In a possible configuration, the stream inlet (25) of a reactor shell (20) extends outward from a side surface of the reactive stream duct (22). The stream outlet of a reactor shell (20) extends outward from another side surface that is at the opposite side of the stream inlet (25). The stream inlet (25) extends along a first imaginary line and the stream outlet (26) extend along a second imaginary line that is parallel to the first imaginary line. Thus, the modular setup of the cascaded reactor system (10) can be realized by means of connecting the stream outlet (26) of the preceding reactor shell (20) with the stream inlet (25) of the following reactor shell (20), forming a reactive stream duct (22) in a continuous pipeline whose length can be determined flexibly in accordance with the desired endothermic reaction yield, therefore leading to a scaled-up reactor system that is easier to assemble and perform maintenance thereon. This preferred configuration allows scaling up of a system for carrying on an endothermic reaction in a compact way, such that the plurality of reactor shells (20) can be connected to each other serially in a vertical manner, allowing increased endothermic reaction yield per floor area that is occupied by a reactor system, much lower land footprint.

[0065] Each reactor shell (20), comprises an inlet chamber (28) between the stream inlet (25) and the catalyst section (21). Said inlet chamber is divided by a dividing device into a cold section and an inlet section. Electrical feeds (51) are entering the pressure vessel within the cold section of said inlet chamber (28).

[0066] In a possible embodiment, said cold section (281) is accessible from a sealed flange (29) within the pressure vessel (reactor shell (20)). This allows easier access to the electrical connections through the removable sealing flange (29) in case of the need for maintenance or inspection, as well as allowing to perform such a task at each individual reactor shell (20) separately.

[0067] Stream inlets (25) and stream outlets (26) have matching structure that allows connecting to each other.

[0068] Additionally, in a possible embodiment, any individual reactor shell (20) among the serially connected plurality of such may have same or different specifications compared to the any individual reactor shell (20) for process optimization reasons, if desired. This allows an additional freedom for design optimization while scaling-up the system to carrying out an endothermic reaction.

[0069] Furthermore, the cascaded reactor system (10) comprises an insulation filling (60) that is at least partially encompassing the internal sections of the said plurality of reactor shells (10) along the entirety of the reactive stream duct (22), and configured in a way to not cause any obstruction to the flow of the reactive gas stream.

[0070] The catalytically active species supported on the structured ceramic catalyst bed (30) are transition metals of the d-block elements and / or combination of two or more active species possibly including alkali metals. The structured ceramic catalyst bed (30) may undergo heterogeneous catalyst preparation as incipient wetness impregnation and / or impregnation and / or support wash coating and / or in-situ synthesis that are traditionally used in the synthesis of heterogeneous catalysts.

[0071] In a possible embodiment the electrical heating means (40) is arranged at the structured ceramic catalytic bed (30) within the hollow flow paths (31) so that the catalyst bed (30) is heated from inside. In detail, in a possible embodiment, the electrical heating means (40) is meandered (comprising meandered sections (41)) through some or all of the hollow flow paths (31). Thanks to this embodiment, the hollow flow paths (31) are heated up by the electrical heating means (40) so that the structured ceramic catalyst bed (30) is heated from inside. The physical proximity (or contact) of the electrical heating means (40) with the structure ceramic catalyst bed (30) and the direct contact with the reactive mixture stream enhances the heat transfer via irradiation, convection, and conduction. The proximity will make it possible to operate the structured ceramic catalyst bed (30) at temperature between 300 °C to 1300 °C.

[0072] Thanks to the arrangement of the cascaded reactor system (20) in which it is possible to modularly increase the number of reactor shells (20), it is possible to keep a desired gas space velocity of the reactive stream mixture by providing the same catalyst volume distributed on a multiplicity of relatively short and with relatively small cross section catalyst sections (21). This allows to reduces the mechanical deformation and the risk of shortcutting of the electrical heating means (41) and provides an even distribution of the reactive mixture stream.

[0073] The invention is also disclosing a method for carrying out an endothermic reaction utilizing the above described cascaded reactor system (10) comprising a plurality of reactor shells (20) connected in series, where a fed reactive stream flowing downstream is to be subjected to catalytic reaction when it interacts with the series of structured ceramic catalytic beds (30) along the entirety of the reactive stream duct (22). The method comprises the steps of:

[0074] I) operating power supply (50) for providing electrical energy to the electrically heating means

[0075] (40) in each reactor shell (20) of the cascaded reactor system (10),

[0076] II) feeding reactive mixture stream to stream inlet (25) of a first reactor shell in the series.

[0077] In particular, electrical energy is provided with the power supply (50) through the electrical feeds (51) to the electrical heating means (41) of each of the individual reactor shell (20) of the plurality of such, so that the structured ceramic catalyst bed (30) located at each reactor shell (20) is heated up. The reactive mixture stream is fed to the first reactor shell (20) in series allowing the reactive stream mixture to pass through the hollow flow paths (31) of all of the structured ceramic catalyst beds (30) located in series along the reactive stream duct (22). The reactive mixture stream is allowed to pass from the stream outlet (26) of the last reactor shell (20) in series.

[0078] The reactive mixture is a mixture of a nebulized liquid and / or gas hydrocarbon and / or methane- containing, and / or of a water steam, and / or of an oxidant stream and / or carbon dioxide and / or hydrogen and / or ammonia and / or volatile organic compounds (VOC).

[0079] The reactive mixture stream is fed to the cascaded reactor system (10) at the stream inlet (25) of the first reactor shell (20) in series at a temperature ranging from 25°C to 700°C and a pressure ranging from 1 and 150 bar.

[0080] In each of the reactor shells (20) the reactive mixture stream enters to the reactive stream duct (22) from the stream inlet (25) and fed through the hollow flow paths (31) located between the structured ceramic catalyst bed (30) and the electrical heating means (40) simultaneously reacting on the active phase of the catalyst and being heated up by the heat provided by the electrical heating means (40) up to temperature between 300°C and 1300°C.

[0081] In each of the reactor shells (20) in series the reactive mixture stream passes from the stream outlet (26) of the previous unit to the stream inlet (26) of the next unit in series at a temperature that can be modulated by controlling separately the power supply (50) of each reactor shell (20).

[0082] Electrical connection between cold section (281) and electrically heated ceramic catalyst bed (30) is done via conducting bars (52) passing through the separating device between cold section (281) and stream inlet (25).

[0083] The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

Claims

CLAIMS1. A cascaded reactor system (10) to carry out an endothermic reaction of a reactive mixture stream to be converted to a product gas or product stream characterized in that comprising at least two reactor shells (20) connected in series, so that a stream outlet (26) of a first reactor shell (20) is directly connected to a reactor inlet (25) of a second reactor shell (20) and, where each reactor shell comprises at least one reactive stream duct (22), the stream inlet (25) for receiving the fed reactive mixture stream, the stream outlet (26), a catalyst section (21) provided inside said reactive stream duct (22) between said stream inlet (25) and stream outlet (26); an insulation filling (60) at least partly encompassing said reactive stream duct (22), a catalyst bed (30) accommodated in said catalyst section (21), where the reactive mixture stream undergoes a catalytic reaction, electrical heating means (40) for heating said ceramic catalyst bed (30) up to a predetermined reaction temperature; at least two electrical feeds (51) passing through the inlet section connected to an electrical power supply (50) provided outside of the reactive stream duct (22), and- wherein the stream inlet (25) of at least one reactor shell (20) contains a separating device (282) for creating a cold section (281) within the inlet zone of said reactor shell (20) wherein the electric feeds that bring electricity into the reactor shell (20) are at least partly located within said cold section for preventing said electric feeds from exposition to high temperatures.

2. The reactor system according to claim 1 , wherein the electric feeds that bring electricity into said reactor shell (20) are at least partly located within said cold section (281) for preventing said electric feeds from exposition to high temperatures.

3. The reactor system according to any of claim 1 to 2, wherein the separating device (282) between stream inlet (25) and cold section (281) is made out of an insulating material.

4. The reactor system according to any of claim 1 to 3, the reactor shell (20) comprising flanged connection allowing the cold section to be accessible via a flanged connection on the reactor shell (20) for fast access and maintenance of the electrical system located within the cold section.

5. The reactor system according to any of claim 1 to 4, wherein the electrical connection between cold section (281) and electrically heated ceramic catalyst bed (30) is done via conducting bars (52) passing through the separating device between cold section (281) and stream inlet (25).

6. The reactor system according to any of claim 1 to 5, wherein the design pressure of the reactor system is between 1 - 150 bar.

7. The reactor system according to any of claim 1 to 5, wherein the electrical heating means (40) and the electrical power supply (50) are configured to heat the ceramic catalyst bed (30) up to a temperature between 300°C and 1300°C.

8. The reactor system according to any of claim 1 to 7, wherein individual pressure vessels are connected together via welding or flanged connections.

9. The reactor system according to any of claim 1 to 10, wherein the said electrical heating means (40) is a resistive wire.

10. A method for carrying out an endothermic reaction using a cascaded reactor system (10) such as in one of the claims 1-11 , characterized in that comprising the steps of: operating power supply (50) for providing electrical energy to the electrically heating means (40) in each reactor shell (20) of the cascaded reactor system (10),- feeding reactive mixture stream to stream inlet (25) of a first reactor shell in the series.

11. In accordance with the method of Claim 10, wherein the reactive mixture stream is selected from the group consisting of a mixture of a nebulized liquid and / or gas hydrocarbon, methane-containing compounds, water steam, oxidant stream, carbon dioxide, hydrogen, ammonia, volatile organic compounds (VOC), and combinations thereof.

12. In accordance with the method of Claim 10, further comprising the step of regulating the pressure within the cascaded reactor system to be within the range of 1 to 150 bar.

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